1.
Regulation of therapeutic goods
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The regulation of therapeutic goods, that is drugs and therapeutic devices, varies by jurisdiction. In some countries, such as the United States, they are regulated at the level by a single agency. In other jurisdictions they are regulated at the level, or at both state and national levels by various bodies, as is the case in Australia. The role of therapeutic goods regulation is designed mainly to protect the health, regulation is aimed at ensuring the safety, quality, and efficacy of the therapeutic goods which are covered under the scope of the regulation. In most jurisdictions, therapeutic goods must be registered before they are allowed to be marketed, there is usually some degree of restriction of the availability of certain therapeutic goods depending on their risk to consumers. Therapeutic goods in Australia are regulated by the Therapeutic Goods Administration, there are 5 main categories, Normal Medicines - Cough, cold and fever medicines, antiseptics, vitamins and others. Sold freely in pharmacies and some large supermarkets, red Stripe Medicines - These medicines are sold only with medical prescription. Antibiotics, Anti allergenics, Anti inflammatories, and other medicines, in Brazil, governmental control is loose on this type, it is not uncommon to buy this type of prescription medicine over the counter without a prescription. Red Stripe Psychoactive Medicines - These medicines are only with a Special Control white medical prescription with carbon copy. The original must be retained by the pharmacist after the sale, Drugs include anti-depressants, anti-convulsants, some sleep aids, anti-psychotics and other non-habit-inducing controlled medicines. Though some consider them habit inducing, anabolic steroids are also regulated under this category, black Stripe Medicines - These medicines are sold only with the Blue B Form medical prescription, which is valid for 30 days and must be retained by the pharmacist after the sale. Includes sedatives, some anorexic inducers and other habit-inducing controlled medicines, includes amphetamines and other stimulants, opioids and other strong habit-forming controlled medicines. In Canada, regulation of goods are governed by the Food and Drug Act. In addition, the Controlled Drugs and Substances Act requires additional regulatory requirements for controlled drugs, the regulation of drugs in Burma is governed by the Food and Drug Administration and Food and Drug Board of Authority. The regulation of drugs in China is governed by the China Food, Medicines for Human Use in the United Kingdom are regulated by the Medicines and Healthcare products Regulatory Agency. The availability of drugs is regulated by classification by the MHRA as part of marketing authorisation of a product, Medicines in the Republic of Ireland are regulated according to the Misuse of Drugs Regulations 1988. Controlled drugs are divided into five categories based on their potential for misuse, cD1, cannabis, lysergamide, coca leaf, etc. Use prohibited except in limited circumstances where a license has been granted, CD2, amphetamine, methadone, morphine, fentanyl, oxycodone, tapentadol, etc
2.
PubChem
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PubChem is a database of chemical molecules and their activities against biological assays. The system is maintained by the National Center for Biotechnology Information, a component of the National Library of Medicine, PubChem can be accessed for free through a web user interface. Millions of compound structures and descriptive datasets can be downloaded via FTP. PubChem contains substance descriptions and small molecules with fewer than 1000 atoms and 1000 bonds, more than 80 database vendors contribute to the growing PubChem database. PubChem consists of three dynamically growing primary databases, as of 28 January 2016, Compounds,82.6 million entries, contains pure and characterized chemical compounds. Substances,198 million entries, contains also mixtures, extracts, complexes, bioAssay, bioactivity results from 1.1 million high-throughput screening programs with several million values. PubChem contains its own online molecule editor with SMILES/SMARTS and InChI support that allows the import and export of all common chemical file formats to search for structures and fragments. In the text search form the database fields can be searched by adding the name in square brackets to the search term. A numeric range is represented by two separated by a colon. The search terms and field names are case-insensitive, parentheses and the logical operators AND, OR, and NOT can be used. AND is assumed if no operator is used, example,0,5000,50,10 -5,5 PubChem was released in 2004. The American Chemical Society has raised concerns about the publicly supported PubChem database and they have a strong interest in the issue since the Chemical Abstracts Service generates a large percentage of the societys revenue. To advocate their position against the PubChem database, ACS has actively lobbied the US Congress, soon after PubChems creation, the American Chemical Society lobbied U. S. Congress to restrict the operation of PubChem, which they asserted competes with their Chemical Abstracts Service
3.
Guide to Pharmacology
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The IUPHAR/BPS Guide to PHARMACOLOGY is an open-access website, acting as a portal to information on the biological targets of licensed drugs and other small molecules. The Guide to PHARMACOLOGY is developed as a joint venture between the International Union of Basic and Clinical Pharmacology and the British Pharmacological Society and this replaces and expands upon the original 2009 IUPHAR Database. The information featured includes pharmacological data, target and gene nomenclature, overviews and commentaries on each target family are included, with links to key references. The Guide to PHARMACOLOGY was initially made available online in December 2011 with additional material released in July 2012 and its network of over 700 specialist advisors contribute expertise and data. The current PI and Grant holder of the GtoPdb project is Prof. Jamie A. Davies, the development and release of the first version of the GtoPdb in 2012 was described in an editorial published in the British Journal of Pharmacology entitled Guide to Pharmacology. org- an update. The IUPHAR-DB is no longer being developed and all the contained within this site is now available through the Guide to PHARMACOLOGY. A complete list of all the approved drugs included on the website is available via the ligand list. The Guide to PHARMACOLOGY is being expanded to include information on targets and ligands. Search features on the website include quick and advanced search options, other features include Hot topic news items and a recent receptor-ligand pairing list. A hard copy summary of the database is published as The Concise Guide to Pharmacology 2015/2016 as a series of papers as a bi-annual supplement to the British Journal of Pharmacology. The Guide to PHARMACOLOGY includes links to other relevant resources via target, many of these resources maintain reciprocal links with the relevant Guide to PHARMACOLOGY pages. As of November 2015 the Wellcome Trust is supporting a new project to develop the Guide to Immumopharmacology, the latter continues to be supported by the British Pharmacological Society
4.
ChemSpider
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ChemSpider is a database of chemicals. ChemSpider is owned by the Royal Society of Chemistry, the database contains information on more than 50 million molecules from over 500 data sources including, Each chemical is given a unique identifier, which forms part of a corresponding URL. This is an approach to develop an online chemistry database. The search can be used to widen or restrict already found results, structure searching on mobile devices can be done using free apps for iOS and for the Android. The ChemSpider database has been used in combination with text mining as the basis of document markup. The result is a system between chemistry documents and information look-up via ChemSpider into over 150 data sources. ChemSpider was acquired by the Royal Society of Chemistry in May,2009, prior to the acquisition by RSC, ChemSpider was controlled by a private corporation, ChemZoo Inc. The system was first launched in March 2007 in a release form. ChemSpider has expanded the generic support of a database to include support of the Wikipedia chemical structure collection via their WiChempedia implementation. A number of services are available online. SyntheticPages is an interactive database of synthetic chemistry procedures operated by the Royal Society of Chemistry. Users submit synthetic procedures which they have conducted themselves for publication on the site and these procedures may be original works, but they are more often based on literature reactions. Citations to the published procedure are made where appropriate. They are checked by an editor before posting. The pages do not undergo formal peer-review like a journal article. The comments are moderated by scientific editors. The intention is to collect practical experience of how to conduct useful chemical synthesis in the lab, while experimental methods published in an ordinary academic journal are listed formally and concisely, the procedures in ChemSpider SyntheticPages are given with more practical detail. Comments by submitters are included as well, other publications with comparable amounts of detail include Organic Syntheses and Inorganic Syntheses
5.
Chemical formula
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These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH
6.
Jmol
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Jmol is computer software for molecular modelling chemical structures in 3-dimensions. Jmol returns a 3D representation of a molecule that may be used as a teaching tool and it is written in the programming language Java, so it can run on the operating systems Windows, macOS, Linux, and Unix, if Java is installed. It is free and open-source software released under a GNU Lesser General Public License version 2.0, a standalone application and a software development kit exist that can be integrated into other Java applications, such as Bioclipse and Taverna. A popular feature is an applet that can be integrated into web pages to display molecules in a variety of ways, for example, molecules can be displayed as ball-and-stick models, space-filling models, ribbon diagrams, etc. Jmol supports a range of chemical file formats, including Protein Data Bank, Crystallographic Information File, MDL Molfile. There is also a JavaScript-only version, JSmol, that can be used on computers with no Java, the Jmol applet, among other abilities, offers an alternative to the Chime plug-in, which is no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS9. Jmol requires Java installation and operates on a variety of platforms. For example, Jmol is fully functional in Mozilla Firefox, Internet Explorer, Opera, Google Chrome, fast and Scriptable Molecular Graphics in Web Browsers without Java3D
7.
Simplified molecular-input line-entry system
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The simplified molecular-input line-entry system is a specification in form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules, the original SMILES specification was initiated in the 1980s. It has since modified and extended. In 2007, a standard called OpenSMILES was developed in the open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. The Environmental Protection Agency funded the project to develop SMILES. It has since modified and extended by others, most notably by Daylight Chemical Information Systems. In 2007, a standard called OpenSMILES was developed by the Blue Obelisk open-source chemistry community. Other linear notations include the Wiswesser Line Notation, ROSDAL and SLN, in July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is generally considered to have the advantage of being slightly more human-readable than InChI, the term SMILES refers to a line notation for encoding molecular structures and specific instances should strictly be called SMILES strings. However, the term SMILES is also used to refer to both a single SMILES string and a number of SMILES strings, the exact meaning is usually apparent from the context. The terms canonical and isomeric can lead to confusion when applied to SMILES. The terms describe different attributes of SMILES strings and are not mutually exclusive, typically, a number of equally valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol, algorithms have been developed to generate the same SMILES string for a given molecule, of the many possible strings, these algorithms choose only one of them. This SMILES is unique for each structure, although dependent on the algorithm used to generate it. These algorithms first convert the SMILES to a representation of the molecular structure. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database, there is currently no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, and these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES
8.
Drug
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A drug is any substance that, when inhaled, injected, smoked, consumed, absorbed via a patch on the skin, or dissolved under the tongue, causes a physiological change in the body. In pharmacology, a drug, also called a medication or medicine, is a chemical substance used to treat, cure, prevent. Traditionally drugs were obtained through extraction from plants, but more recently also by organic synthesis. Pharmaceutical drugs may be used for a duration, or on a regular basis for chronic disorders. Another major classification system is the Biopharmaceutics Classification System and this classifies drugs according to their solubility and permeability or absorption properties. Psychoactive drugs are chemical substances that affect the function of the nervous system, altering perception. They include alcohol, a depressant, and the nicotine and caffeine. These three are the most widely consumed psychoactive drugs worldwide and are also considered recreational drugs since they are used for rather than medicinal purposes. Other recreational drugs include hallucinogens, opiates and amphetamines and some of these are used in spiritual or religious settings. Some drugs can cause addiction and all drugs can have side effects, excessive use of stimulants can promote stimulant psychosis. Many recreational drugs are illicit and international such as the Single Convention on Narcotic Drugs exist for the purpose of their prohibition. The transitive verb to drug arose later and invokes the psychoactive rather than properties of a substance. A medication or medicine is a drug taken to cure or ameliorate any symptoms of an illness or medical condition, the use may also be as preventive medicine that has future benefits but does not treat any existing or pre-existing diseases or symptoms. In the United Kingdom, behind-the-counter medicines are called pharmacy medicines which can only be sold in registered pharmacies and these medications are designated by the letter P on the label. The range of medicines available without a prescription varies from country to country, medications are typically produced by pharmaceutical companies and are often patented to give the developer exclusive rights to produce them. Those that are not patented are called generic drugs since they can be produced by other companies without restrictions or licenses from the patent holder, pharmaceutical drugs are usually categorised into drug classes. A group of drugs will share a chemical structure, or have the same mechanism of action. Another major classification system is the Biopharmaceutics Classification System and this groups drugs according to their solubility and permeability or absorption properties
9.
Binding selectivity
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Binding selectivity is defined with respect to the binding of ligands to a substrate forming a complex. A selectivity coefficient is the constant for the reaction of displacement by one ligand of another ligand in a complex with the substrate. Binding selectivity is of importance in biochemistry and in chemical separation processes. The concept of selectivity is used to quantify the extent to which a substrate, A. The simplest case is where the complexes formed have 1,1 stoichiometry, then, the two interactions may be characterized by equilibrium constants KAB and KAC. A + B ↽ − − ⇀ AB, K AB = A + C ↽ − − ⇀ AC, a selectivity coefficient is defined as the ratio of the two equilibrium constants. The greater the selectivity coefficient, the more the ligand C will displace the ligand B from the complex formed with the substrate A, an alternative interpretation is that the greater the selectivity coefficient, the lower the concentration of C that is needed to displace B from AB. Selectivity coefficients are determined experimentally by measuring the two constants, KAB and KAC. In biochemistry the substrate is known as a receptor, a receptor is a protein molecule, embedded in either the plasma membrane or the cytoplasm of a cell, to which one or more specific kinds of signalling molecules may bind. A ligand may be a peptide or another small molecule, such as a neurotransmitter, a hormone, the specificity of a receptor is determined by its spatial geometry and the way it binds to the ligand through non-covalent interactions, such as hydrogen bonding or Van der Waals forces. If a receptor can be isolated a synthetic drug can be developed either to stimulate the receptor, an agonist or to block it, the stomach ulcer drug cimetidine was developed as an H2 antagonist by chemically engineering the molecule for maximum specificity to an isolated tissue containing the receptor. The further use of quantitative structure-activity relationships led to the development of agents such as ranitidine. It is important to note that selectivity when referring to a drug is relative, for example, in a higher dose, a specific drug molecule may also bind to other receptors than those said to be selective. Chelation therapy is a form of treatment in which a chelating ligand is used to selectively remove a metal from the body. Selectivity is determined by various factors and it also forms stronger complexes with oxygen-donor ligands than with nitrogen-donor ligands. Deferoxamine, a naturally occurring siderophore produced by the actinobacter Streptomyces pilosus and was used initially as a chelation therapy agent, synthetic siderophores such as deferiprone and deferasirox have been developed, using the known structure of deferoxamine as a starting point. Chelation occurs with the two oxygen atoms, wilsons disease is caused by a defect in copper metabolism which results in accumulation of copper metal in various organs of the body. The target ion in this case is divalent, Cu2+ and this ion is classified as borderline in the scheme of Ahrland, Chatt and Davies
10.
5-HT1A receptor
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The 5-HT1A receptor is a subtype of 5-HT receptor that binds the endogenous neurotransmitter serotonin. It is a G protein-coupled receptor that is coupled to Gi/Go, HTR1A denotes the human gene encoding for the receptor. The 5-HT1A receptor is the most widespread of all the 5-HT receptors, the 5-HT1A receptors in the raphe nucleus are largely somatodendritic autoreceptors, whereas those in other areas such as the hippocampus are postsynaptic receptors. 5-HT1A receptor agonists are involved in neuromodulation and they decrease blood pressure and heart rate via a central mechanism, by inducing peripheral vasodilation, and by stimulating the vagus nerve. These effects are the result of activation of 5-HT1A receptors within the ventrolateral medulla. Vasodilation of the vessels in the skin via central 5-HT1A activation increases heat dissipation from the organism out into the environment. Others such as gepirone, flesinoxan, flibanserin, and naluzotan have also been investigated, 5-HT1A receptor activation likely plays a significant role in the positive effects of serotonin releasing agents like MDMA as well. 5-HT1A receptors in the raphe nucleus are co-localized with neurokinin 1 receptors and have been shown to inhibit the release of substance P. Consequently, novel NK1 receptor antagonists are now in use for the treatment of nausea and emesis, as mentioned above, some of the atypical antipsychotics are 5-HT1A receptor partial agonists, and this property has been shown to enhance their clinical efficacy. Enhancement of dopamine release in these areas may also play a role in the antidepressant. Activation of 5-HT1A receptors has been demonstrated to impair certain aspects of memory and learning, by inhibiting the release of glutamate, 5-HT1A activation are known to improve cognitive functions associated with the prefrontal cortex, possibly via inducing prefrontal cortex dopamine and acetylcholine release. The receptor does not affect vasopressin or renin secretion, unlike the 5-HT2 receptors and it has been suggested that oxytocin release may contribute to the prosocial, antiaggressive, and anxiolytic properties observed upon activation of the receptor. β-Endorphin secretion may contribute to antidepressant, anxiolytic, and analgesic effects, 5-HT1A receptors can be located on the cell body, dendrites, axons, and both presynaptically and postsynaptically in nerve terminals or synapses. Those located on the soma and dendrites are referred to as somatodendritic, stimulation of 5-HT1A autoreceptors inhibits the release of serotonin in nerve terminals. This autoreceptor-mediated inhibition of serotonin release has been theorized to be a factor in the therapeutic lag that is seen with serotonergic antidepressants such as the SSRIs. The autoreceptors must first densensitize before the concentration of serotonin in the synapse can become elevated appreciably. Though the responsiveness of the autoreceptors is somewhat reduced with chronic treatment, unlike most drugs that elevate extracellular serotonin levels like the SSRIs and MAOIs, SRAs such as fenfluramine and MDMA bypass serotonin autoreceptors such as 5-HT1A. They do this by acting on the release mechanisms of serotonin neurons
11.
5-HT1B receptor
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5-hydroxytryptamine receptor 1B also known as the 5-HT1B receptor is a protein that in humans is encoded by the HTR1B gene. The 5-HT1B receptor is a 5-HT receptor subtype, 5-HT1B receptors are widely distributed throughout the CNS with the highest concentrations found in the frontal cortex, basal ganglia, striatum, and the hippocampus. The function of the 5-HT1B receptor differs depending upon its location, in the frontal cortex, it is believed to act as a postsynaptic receptor inhibiting the release of dopamine. In the hippocampus, a recent study has demonstrated that activation of postsynaptic 5-HT1B heteroreceptors produces a facilitation in excitatory synaptic transmission which is altered in depression. When the expression of 5-HT1B in human cortex was traced throughout life, significant changes during adolescence were observed, outside the brain, 5-HT1B receptor activation also has vascular effects, such as pulmonary vasoconstriction. Furthermore, blocking 5-HT1B receptor signalling increases the number of osteoblasts, bone mass, knockout mice lacking the 5-HT1B gene have shown an increase in aggression and a higher preference for alcohol. Under basal conditions, knockout mice present with a normal phenotype, however, after undergoing chronic unpredictable stress treatment to induce a depression-like phenotype these animals do not benefit from administration of selective serotonin reuptake inhibitor. A genetic variant in the region, A-161T, has been examined with respect to personality traits. IUPHAR Database of Receptors and Ion Channels, international Union of Basic and Clinical Pharmacology. Human HTR1B genome location and HTR1B gene details page in the UCSC Genome Browser and this article incorporates text from the United States National Library of Medicine, which is in the public domain
12.
5-HT1D receptor
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5-hydroxytryptamine receptor 1D, also known as HTR1D, is a 5-HT receptor, but also denotes the human gene encoding it. 5-HT1D acts on the nervous system, and affects locomotion. It also induces vascular vasoconstriction in the brain, 5HT1D receptor is a G protein linked receptor that activates an intracellular messenger cascade to produce an inhibitory response by decreasing cellular levels of cAMP. The 5HT1D is a 7-TM receptor, a large intercellular loop between TM-5 and TM-6 is believed to be associated with coupling to a second messenger. Agonists might bind in a manner that utilizes an aspartate residue in TM-3 and residues in the TM-4, TM-5, a human clone containing an intronless open reading frame was found to encode 377 amino acids of the 5HT1D receptor. The gene has been localized on chromosome 1, region 1p34. 3-36.3 Molecular modelling has provided a picture of the binding site of 5HT1D. The amino acid residues within the binding site region have been identified. This is a guide to design potential 5HT1D receptor agonists. When sumatriptan binds there is major conformational change in both ligand and receptor in the binding pocket, IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology, human HTR1D genome location and HTR1D gene details page in the UCSC Genome Browser. This article incorporates text from the United States National Library of Medicine, which is in the public domain
13.
5-HT1E receptor
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5-hydroxytryptamine 1E receptor is a highly expressed human G-protein coupled receptor that belongs to the 5-HT1 receptor family. The human gene is denoted as HTR1E, the function of the 5-HT1E receptor is unknown due to the lack of selective pharmacological tools, specific antibodies, and permissive animal models. This receptor is unique among the serotonin receptors in that it is not known to be expressed by rats or mouse species, however the genomes of the pig, rhesus monkey, and several lagomorphs as well as the guinea pig each encode a homologous 5-HT1E receptor gene. The guinea pig is the most likely candidate for study of 5-HT1E receptor function in vivo. The expression of 5-HT1E receptors in the guinea pig brain has been confirmed, 5-HT1E receptor expression patterns of the human. In the human cortex, the expression of 5-HT1E undergoes a transition during adolescence. The most closely related receptor to the 5-HT1E is the 5-HT1F receptor and they share 57% amino acid sequence homology and have some pharmacological characteristics in common. Both receptors are Gi-coupled and both receptors have high affinities for 5-HT and low affinities for 5-carboxyamidotryptaine and mesulergine, however, due to major differences in brain expression patterns, these receptors are unlikely to mediate similar functions in humans. For example, 5-HT1E receptors are abundant in the hippocampus but are not detectable in the striatum, thus, conclusions about the function of the 5-HT1E receptor cannot be ascribed to the function of the 5-HT1F receptor, and vice versa. No highly selective 5-HT1E ligands are available yet, 5-HT remains the only radioligand available with high affinity for the 5-HT1E receptor. BRL-54443 - mixed 5-HT1E/1F agonist None as yet, 5-HT1 receptor 5-HT receptor Human HTR1E genome location and HTR1E gene details page in the UCSC Genome Browser. This article incorporates text from the United States National Library of Medicine, which is in the public domain
14.
5-HT1F receptor
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5-hydroxytryptamine receptor 1F, also known as HTR1F is a 5-HT1 receptor protein and also denotes the human gene encoding it. IUPHAR Database of Receptors and Ion Channels, international Union of Basic and Clinical Pharmacology. Human HTR1F genome location and HTR1F gene details page in the UCSC Genome Browser and this article incorporates text from the United States National Library of Medicine, which is in the public domain
15.
Receptor antagonist
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A receptor antagonist is a type of receptor ligand or drug that blocks or dampens agonist-mediated responses rather than provoking a biological response itself upon binding to a receptor. They are sometimes called blockers, examples include alpha blockers, beta blockers, antagonist activity may be reversible or irreversible depending on the longevity of the antagonist–receptor complex, which, in turn, depends on the nature of antagonist–receptor binding. The majority of drug antagonists achieve their potency by competing with endogenous ligands or substrates at structurally defined binding sites on receptors, biochemical receptors are large protein molecules that can be activated by the binding of a ligand. Receptors can be membrane-bound, occurring on the membrane, or intracellular. Binding occurs as a result of noncovalent interaction between the receptor and its ligand, at locations called the site on the receptor. A receptor may contain one or more binding sites for different ligands, binding to the active site on the receptor regulates receptor activation directly. The activity of receptors can also be regulated by the binding of a ligand to other sites on the receptor, antagonists mediate their effects through receptor interactions by preventing agonist-induced responses. This may be accomplished by binding to the site or the allosteric site. In addition, antagonists may interact at unique binding sites not normally involved in the regulation of the receptors activity to exert their effects. The term antagonist was originally coined to describe different profiles of drug effects, the biochemical definition of a receptor antagonist was introduced by Ariens and Stephenson in the 1950s. The current accepted definition of receptor antagonist is based on the receptor occupancy model and it narrows the definition of antagonism to consider only those compounds with opposing activities at a single receptor. Agonists were thought to turn on a cellular response by binding to the receptor. Antagonists were thought to turn off that response by blocking the receptor from the agonist and this definition also remains in use for physiological antagonists, substances that have opposing physiological actions, but act at different receptors. Our understanding of the mechanism of drug-induced receptor activation and receptor theory, the two-state model of receptor activation has given way to multistate models with intermediate conformational states. This means efficacy may actually depend on where that receptor is expressed, by definition, antagonists display no efficacy to activate the receptors they bind. Antagonists do not maintain the ability to activate a receptor, once bound, however, antagonists inhibit the function of agonists, inverse agonists, and partial agonists. In functional antagonist assays, a dose-response curve measures the effect of the ability of a range of concentrations of antagonists to reverse the activity of an agonist, the potency of an antagonist is usually defined by its half maximal inhibitory concentration IC50 value. This can be calculated for a given antagonist by determining the concentration of antagonist needed to elicit half inhibition of the biological response of an agonist
16.
5-HT2A receptor
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The mammalian 5-HT2A receptor is a subtype of the 5-HT2 receptor that belongs to the serotonin receptor family and is a G protein-coupled receptor. This is the main excitatory receptor subtype among the GPCRs for serotonin, although 5-HT2A may also have an effect on certain areas such as the visual cortex. This receptor was first noted for its importance as a target of serotonergic psychedelic drugs such as LSD, later it came back to prominence because it was also found to be mediating, at least partly, the action of many antipsychotic drugs, especially the atypical ones. 5-HT2A may be a receptor for the spread of the human polyoma virus called JC virus. Downregulation of post-synaptic 5-HT2A receptor is an adaptive process provoked by chronic administration of selective serotonin reuptake inhibitors, deceased suicidal and otherwise depressed patients have had more 5-HT2A receptors than normal patients. These findings suggest that post-synaptic 5-HT2A overdensity is involved in the pathogenesis of depression, 5-HT2A is thought to correspond to what was originally described as D subtype of 5-HT receptors by Gaddum and Picarelli. Later it was shown that the 5-HT2 was very close to 5-HT1C and thus were clubbed together, thus the 5-HT2 receptor family is composed of three separate molecular entities, the 5-HT2A, the 5-HT2B and the 5-HT2C receptors. 5-HT2A is expressed throughout the central nervous system. It is expressed near most of the serotoninergic terminal rich areas, including neocortex, in the rat cerebellum, the protein has also been found in the Golgi cells of the granular layer, and in the Purkinje cells. In the periphery, it is expressed in platelets and many cell types of the cardiovascular system, in fibroblasts. Additionally, 5-HT2A mRNA expression has been observed in human monocytes, the 5-HT2A receptor is known primarily to couple to the Gαq signal transduction pathway. Upon receptor stimulation with agonist, Gαq and β-γ subunits dissociate to initiate downstream effector pathways, Gαq stimulates phospholipase C activity, which subsequently promotes the release of diacylglycerol and inositol triphosphate, which in turn stimulate protein kinase C activity and Ca2+ release. Other 5-HT2A agonists like LSD also have potent anti-inflammatory effects against TNF-alpha-induced inflammation, activation of the 5-HT2A receptor in hypothalamus causes increases in hormonal levels of oxytocin, prolactin, ACTH, corticosterone, and renin. A very large family of derivatives from these three classes has been developed, and their structure-activity relationships have been extensively researched, agonists acting at 5-HT2A receptors located on the apical dendrites of pyramidal cells within regions of the prefrontal cortex are believed to mediate hallucinogenic activity. Newer findings reveal that psychoactive effects of classic psychedelics are mediated by the receptor heterodimer 5-HT2A–mGlu2, agonists enhance dopamine in PFC, enhances memory and plays an active role in attention and learning. O-4310, 5-HT2A selective, claimed to have 100x selectivity over 5-HT2C and be inactive at 5-HT2B PHA-57378, dual 5-HT2A / 5-HT2C agonist, anxiolytic effects in animal studies. 25C-NBOMe Methysergide, a congener of methylergonovine, used in treatment of migraine blocks 5-HT2A and 5-HT2C receptors, oSU-6162 acts as a partial agonist at both 5-HT2A and dopamine D2 receptors 25CN-NBOH, 100x selectivity for 5-HT2A over 5-HT2C, 46x selectivity over 5-HT2B. Efavirenz, a drug, produces psychiatric side effects thought to be mediated by 5-HT2A
17.
5-HT2B receptor
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5-Hydroxytryptamine receptor 2B also known as serotonin receptor 2B is a protein that in humans is encoded by the HTR2B gene. 5-HT2B is a member of the 5-HT2 receptor family that binds the neurotransmitter serotonin, the 5-HT2 receptors mediate many of the central and peripheral physiologic functions of serotonin. The 5-HT2B receptor stimulation can also lead to proliferation of cardiac valves fibroblasts. 5-HT2B receptors have also strongly implicated in drug-induced valvular heart disease. In this context, it is considered to be an antitarget. The structure of the 5-HT2B receptor was recently solved in complex with the valvulopathogenic drug ergotamine, as of 2009, few highly selective 5-HT2B receptor ligands have been discovered, although numerous potent non-selective compounds are known, particularly agents with concomitant 5-HT2C binding. Selective BW-723C86, fair functional subtype selectivity, almost full agonist, MDMA MDA MEM Pergolide Cabergoline Norfenfluramine Chlorphentermine Aminorex mCPP Bromo-dragonfly DMT 5-MeO-DMT LSD-25 - About equal affinity for human cloned 5-HT2B and 5-HT2A receptors. Psilocin Agomelatine - primarily a melatonin Mt1/Mt2 receptor agonist, with a less potent antagonism of 5-HT2B, more recent research has focused on possible application of 5-HT2B antagonists as treatments for chronic heart disease. Research claims serotonin 5-HT2B receptors have effect on liver regeneration, IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology, human HTR2B genome location and HTR2B gene details page in the UCSC Genome Browser. This article incorporates text from the United States National Library of Medicine, which is in the public domain
18.
5-HT2C receptor
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The 5-HT2C receptor is a subtype of 5-HT receptor that binds the endogenous neurotransmitter serotonin. It is a G protein-coupled receptor that is coupled to Gq/G11, HTR2C denotes the human gene encoding for the receptor, that in humans is located at the X chromosome. As males have one copy of the gene and in one of the two copies of the gene is repressed, polymorphisms at this receptor can affect the two sexes to differing extent. At the cell surface the receptor exists as a homodimer, 5-HT2C receptors are widely distributed across the periphery and brain in humans. The 5-HT2C receptor is one of the binding sites for serotonin. Activation of this receptor by serotonin inhibits dopamine and norepinephrine release in areas of the brain. 5-HT2C receptors are claimed to significantly regulate mood, anxiety, feeding, 5-HT2C receptors regulate dopamine release in the striatum, prefrontal cortex, nucleus accumbens, hippocampus, hypothalamus, and amygdala, among others. Research indicates that some victims have an abnormally high number of 5-HT2C receptors in the prefrontal cortex. There is some mixed evidence that agomelatine, a 5-HT2C antagonist, is an effective antidepressant, antagonism of 5-HT2C receptors by agomelatine results in an increase of dopamine and norepinephrine activity in the frontal cortex. Many atypical antipsychotics block 5-HT2C receptors, but their use is limited by multiple undesirable actions on various neurotransmitters and receptors. Fluoxetine acts as a direct 5-HT2C antagonist in addition to inhibiting serotonin reuptake, however, an overactivity of 5-HT2C receptors may contribute to depressive and anxiety symptoms in a certain population of patients. Activation of 5-HT2C by serotonin is responsible for many of the side effects of SSRI and SNRI medications, such as sertraline, paroxetine, venlafaxine. Some of the anxiety caused by SSRIs is due to excessive signalling at 5-HT2C. Over a period of 1–2 weeks, the receptor begins to downregulate, along with the downregulation of 5-HT2A, 5-HT1A and this downregulation parallels the onset of the clinical benefits of SSRIs. 5-HT2C receptors exhibit constitutive activity in vivo, and may retain the ability to influence neurotransmission in the absence of ligand occupancy, thus, 5-HT2C receptors do not require binding by a ligand in order to exhibit influence on neurotransmission. Inverse agonists may be required to fully extinguish 5-HT2C constitutive activity, 5-HT2C receptors mediate the release and increase of extracellular dopamine in response to many drugs, including caffeine, nicotine, amphetamine, morphine, cocaine, and others. 5-HT2C antagonism increases dopamine release in response to reinforcing drugs, feeding, social interaction, and sexual activity all release dopamine subject to inhibition of 5-HT2C. Increased 5-HT2C expression reduces dopamine release in both the presence and absence of stimuli, conditions that increase cytokine levels in the human body may have potential to raise 5-HT2C gene expression in the brain
19.
Ligand (biochemistry)
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In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. In protein-ligand binding, the ligand is usually a molecule which produces a signal by binding to a site on a target protein, the binding typically results in a change of conformation of the target protein. In DNA-ligand binding studies, the ligand can be a molecule, ion. The relationship between ligand and binding partner is a function of charge, hydrophobicity, and molecular structure, the instance of binding occurs over an infinitesimal range of time and space, so the rate constant is usually a very small number. Binding occurs by intermolecular forces, such as bonds, hydrogen bonds. The association of docking is actually reversible through dissociation, measurably irreversible covalent bonding between a ligand and target molecule is atypical in biological systems. In contrast to the definition of ligand in metalorganic and inorganic chemistry, in biochemistry it is whether the ligand generally binds at a metal site. In general, the interpretation of ligand is contextual with regards to what sort of binding has been observed, the etymology stems from ligare, which means to bind. Ligand binding to a receptor protein alters the chemical conformation by affecting the shape orientation. The conformation of a receptor protein composes the functional state, ligands include substrates, inhibitors, activators, and neurotransmitters. The rate of binding is called affinity, and this measurement typifies a tendency or strength of the effect, binding affinity is actualized not only by host-guest interactions, but also by solvent effects that can play a dominant, steric role which drives non-covalent binding in solution. The solvent provides an environment for the ligand and receptor to adapt. Radioligands are radioisotope labeled compounds are used in vivo as tracers in PET studies, the interaction of most ligands with their binding sites can be characterized in terms of a binding affinity. In general, high-affinity binding results in a degree of occupancy for the ligand at its receptor binding site than is the case for low-affinity binding. A ligand that can bind to a receptor, alter the function of the receptor, high-affinity ligand binding implies that a relatively low concentration of a ligand is adequate to maximally occupy a ligand-binding site and trigger a physiological response. The lower the Ki concentration is, the more likely there will be a reaction between the pending ion and the receptive antigen. In the example shown to the right, two different ligands bind to the receptor binding site. Only one of the agonists shown can maximally stimulate the receptor and, thus, an agonist that can only partially activate the physiological response is called a partial agonist
20.
5-HT3 receptor
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This ion channel is cation-selective and mediates neuronal depolarization and excitation within the central and peripheral nervous systems. As with other ligand gated ion channels, the 5-HT3 receptor consists of five subunits arranged around a central ion conducting pore, which is permeable to sodium, potassium, and calcium ions. Binding of the neurotransmitter 5-hydroxytryptamine to the 5-HT3 receptor opens the channel, the rapidly activating, desensitizing, inward current is predominantly carried by sodium and potassium ions. 5-HT3 receptors have a negligible permeability to anions and they are most closely related by homology to the nicotinic acetylcholine receptor. The 5-HT3 receptor differs markedly in structure and mechanism from the other 5-HT receptor subtypes, a functional channel may be composed of five identical 5-HT3A subunits or a mixture of 5-HT3A and one of the other four 5-HT3B, 5-HT3C, 5-HT3D, or 5-HT3E subunits. It appears that only the 5-HT3A subunits form functional homopentameric channels, all other subunit subtypes must heteropentamerize with 5-HT3A subunits to form functional channels. Additionally, there has not currently been any pharmacological difference found between the heteromeric 5-HT3AC, 5-HT3AD, 5-HT3AE, and the homomeric 5-HT3A receptor, the subunits surround a central ion channel in a pseudo-symmetric manner. The 5-HT3 receptor gene is located on human chromosomal region 11q23. 1-q23.2 and it is similar in structure to the mouse gene which has 9 exons and is spread over ~13 kb. Interestingly, four of its introns are exactly in the position as the introns in the homologous α7-Acetylcholine receptor gene. Genes that code for the subunits of the 5-HT3 receptor have been identified, HTR3A and HTR3B for the 5-HT3A and 5-HT3B subunits and in addition HTR3C, HTR3D and HTR3E genes encoding 5-HT3C, 5-HT3D and 5-HT3E subunits. The latter three tend to show peripherally restricted pattern of expression, with levels in the gut. In human duodenum and stomach, for example, 5-HT3C and 5-HT3E mRNA might be greater than for 5-HT3A, there is some evidence to suggest that the 5-HT3 receptor subunits are an important contribution to the effectiveness of these compounds. In patients treated with drugs, certain polymorphism of the HTR3B gene could predict successful antiemetic treatment. This could indicate that the 5-HT3B receptor subunit could be used as biomarker of drug efficacy. HTR3C and HTR3E do not seem to form functional homomeric channels, the pathophysiological role for these additional subunits has yet to be identified. The 5-HT3 receptor is expressed throughout the central and peripheral nervous systems, 5-HT3 receptors are also present on presynaptic nerve terminals. There is some evidence for a role in modulation of neurotransmitter release, 5-HT1 receptor 5-HT2 receptor 5-HT4 receptor 5-HT5 receptor 5-HT6 receptor 5-HT7 receptor 5-HT3 Receptor at the US National Library of Medicine Medical Subject Headings
21.
5-HT5A receptor
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5-Hydroxytryptamine receptor 5A, also known as HTR5A, is a protein that in humans is encoded by the HTR5A gene. This protein has shown to function in part through the regulation of intracellular Ca2+ mobilization. The 5-HT5A receptor has shown to be functional in a native expression system. It also appears to serve as an presynaptic serotonin autoreceptor, the neurotransmitter serotonin has been implicated in a wide range of psychiatric conditions and also has vasoconstrictive and vasodilatory effects. Few highly selective ligands are available for the 5-HT5A receptor. Research in this area is ongoing, valerenic acid, a component of valerian, has been shown to act as a 5HT5A partial agonist. Another ligand that has been recently disclosed is shown below, claimed be a selective 5-HT5A agonist with Ki =124 nM, aSP-5736 AS-2030680 AS-2674723 Latrepirdine Risperidone, moderate 206nM affinity. SB-699,551 5-HT receptor 5-HT1 receptor 5-HT2 receptor 5-HT3 receptor 5-HT4 receptor 5-HT6 receptor 5-HT7 receptor 5-ht5a, IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology, human HTR5A genome location and HTR5A gene details page in the UCSC Genome Browser. This article incorporates text from the United States National Library of Medicine, which is in the public domain
22.
5-HT6 receptor
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The 5-HT6 receptor is a subtype of 5-HT receptor that binds the endogenous neurotransmitter serotonin. It is a G protein-coupled receptor that is coupled to Gs, HTR6 denotes the human gene encoding for the receptor. The 5-HT6 receptor is expressed almost exclusively in the brain, based on its abundance in extrapyramidal, limbic, and cortical regions it can be suggested that the 5-HT6 receptor plays a role in functions like motor control, emotionality, cognition, and memory. Antagonism of 5-HT6 receptors also facilitates dopamine and norepinephrine release in the frontal cortex, despite the 5-HT6 receptor having a functionally excitatory action, it is largely co-localized with GABAergic neurons and therefore produces an overall inhibition of brain activity. 5-HT6 antagonists have also shown to reduce appetite and produce weight loss, and as a result, PRX-07034, BVT-5,182. Additionally, indirect 5-HT6 activation may play a role in the benefits of serotonergic antidepressants like the selective serotonin reuptake inhibitors. A large number of selective 5-HT6 ligands have now been developed, e-6801 E-6837 - partial agonist at rat 5-HT6 receptors. For example, an association between the C267T polymorphism and Alzheimers disease has been shown, others have studied the polymorphism in relation to Parkinsons disease. 5-HT receptor 5-HT1 receptor 5-HT2 receptor 5-HT3 receptor 5-HT4 receptor 5-HT5 receptor 5-HT6, IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology, serotonin 6 receptor at the US National Library of Medicine Medical Subject Headings Human HTR6 genome location and HTR6 gene details page in the UCSC Genome Browser. This article incorporates text from the United States National Library of Medicine, which is in the public domain
23.
5-HT7 receptor
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This receptor has been a drug development target for the treatment of several clinical disorders. The 5-HT7 receptor is encoded by the HTR7 gene, which in humans is transcribed into 3 different splice variants, when the 5-HT7 receptor is activated by serotonin, it sets off a cascade of events starting with release of the stimulatory G protein Gs from the GPCR complex. Gs in turn activates adenylate cyclase which increases intracellular levels of the second messenger cAMP, the 5-HT7 receptor plays a role in smooth muscle relaxation within the vasculature and in the gastrointestinal tract. The highest 5-HT7 receptor densities are in the thalamus and hypothalamus, the 5-HT7 receptor is involved in thermoregulation, circadian rhythm, learning and memory, and sleep. It is also speculated that this receptor may be involved in mood regulation, three splice variants have been identified in humans, which encode receptors that differ in their carboxy terminals. The h5-HT7 is the full length receptor, while the h5-HT7 is truncated at amino acid 432 due to alternative splice donor site, a 5-HT7 splice variant is detectable in rat tissue but is not expressed in humans. Conversely, rats do not express a splice variant homologous to the h5-HT7, drug binding affinities are similar across the three human splice variants, however, inverse agonist efficacies appear to differ between the splice variants. In 1983, evidence for a 5-HT1-like receptor was first found, ten years later, 5-HT7 receptor was cloned and characterized. It has since become clear that the receptor described in 1983 is 5-HT7 and this receptor gene is a candidate locus for involvement in autistic disorder and other neuropsychiatric disorders. Numerous ligands bind to the 5-HT7 receptor with moderate to high affinity, agonists mimic the effects of the endogenous ligand, which is serotonin at the 5-HT7 receptor. Neutral antagonists bind the receptor and have no intrinsic activity but will block the activity of agonists or inverse agonists, inverse agonists inhibit the constitutive activity of the receptor, producing functional effects opposite to those of agonists. Inactivating antagonists are non-competitive antagonists that render the receptor persistently insensitive to agonist, inactivating antagonists all likely interact with the 5-HT7 receptor in an irreversible/pseudo-irreversible manner, as is the case with risperidone. IUPHAR Database of Receptors and Ion Channels, international Union of Basic and Clinical Pharmacology. Human HTR7 genome location and HTR7 gene details page in the UCSC Genome Browser and this article incorporates text from the United States National Library of Medicine, which is in the public domain
24.
5-HT4 receptor
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5-Hydroxytryptamine receptor 4 is a protein that in humans is encoded by the HTR4 gene. This gene is a member of the family of serotonin receptors. The gene product is a transmembrane protein that functions in both the peripheral and central nervous system to modulate the release of various neurotransmitters. Multiple transcript variants encoding proteins with distinct C-terminal sequences have been described, the receptor is located in the alimentary tract, urinary bladder, heart and adrenal gland as well as the central nervous system. It has not been found in the cerebellum, several drugs that act as 5-HT4 selective agonists have recently been introduced into use in both scientific research and clinical medicine. Some drugs that act as 5-HT4 agonists are also active as 5-HT3 antagonists, such as mosapride, metoclopramide, renzapride, and zacopride, research in this area is ongoing. SB-207,145 radiolabeled with carbon-11 is used as a radioligand for 5-HT4 in positron emission tomography pig, bIMU-8 Cisapride CJ-033,466 - partial agonist ML-10302 Mosapride Prucalopride Renzapride RS-67506 RS-67333 - partial agonist SL65. IUPHAR Database of Receptors and Ion Channels, international Union of Basic and Clinical Pharmacology. Human HTR4 genome location and HTR4 gene details page in the UCSC Genome Browser and this article incorporates text from the United States National Library of Medicine, which is in the public domain
25.
Serotonin transporter
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The serotonin transporter also known as the sodium-dependent serotonin transporter and solute carrier family 6 member 4 is a protein that in humans is encoded by the SLC6A4 gene. SERT is a type of transporter protein that transports serotonin from the synaptic cleft to the presynaptic neuron. This transport of serotonin by the SERT protein terminates the action of serotonin and this protein is the target of many antidepressant medications of the SSRI and Tricyclic antidepressant classes. It is a member of the sodium, neurotransmitter symporter family, serotonin-Reuptake transporters are dependent on both the concentration of potassium ion in the cytoplasm and the concentrations of sodium and chloride ions in the extracellular fluid. In order to function properly the Serotonin Transporter requires the potential created by the sodium-potassium adenosine triphosphatase. Right after the release of the Serotonin in the cytoplasm a potassium ion binds to the transporter which is now able to back out returning to its active state. The serotonin transporter removes serotonin from the synaptic cleft back into the synaptic boutons, thus, it terminates the effects of serotonin and simultaneously enables its reuse by the presynaptic neuron. Neurons communicate by using chemical messengers like serotonin between cells, the transporter protein, by recycling serotonin, regulates its concentration in a gap, or synapse, and thus its effects on a receiving neuron’s receptors. The serotonin transporter is also present in platelets, there, serotonin functions as a vasoconstrictive substance and it also serves as a signalling molecule to induce platelet aggregation. SERT spans the plasma membrane 12 times and it belongs to NE, DA, SERT monoamine transporter family. Transporters are important sites for agents that treat psychiatric disorders, drugs that reduce the binding of serotonin to transporters are used to treat mental disorders. The SSRI Fluoxetine and the Tricyclic antidepressant Clomipramine are examples of serotonin reuptake inhibitors, however, studies on SERT showed that tricyclic antidepressants and selective serotonin reuptake inhbitors bind to the central binding site overlapping the substrate binding site. Isosteres 3-cis-indole 8a, Ki =220 pM The gene that encodes the serotonin transporter is called solute carrier family 6, in humans the gene is found on chromosome 17 on location 17q11. 1–q12. These phenotypic changes may, e. g. be increased anxiety, the short variation has 14 repeats of a sequence while the long variation has 16 repeats. The short variation leads to less transcription for SLC6A4, and it has found that it can partly account for anxiety-related personality traits. This polymorphism has been investigated in over 300 scientific studies. The 5-HTTLPR polymorphism may be subdivided further, One study published in 2000 found 14 allelic variants in a group of around 200 Japanese and Caucasian people. In addition to altering the expression of SERT protein and concentrations of serotonin in the brain
26.
PubMed Identifier
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PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby
27.
Agonist
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An agonist is a chemical that binds to a receptor and activates the receptor to produce a biological response. Whereas an agonist causes an action, an antagonist blocks the action of the agonist, receptors can be activated by either endogenous or exogenous agonists, resulting in a biological response. A physiological agonist is a substance that creates the same bodily responses but does not bind to the same receptor, an endogenous agonist for a particular receptor is a compound naturally produced by the body that binds to and activates that receptor. For example, the endogenous agonist for serotonin receptors is serotonin, a superagonist is a compound that is capable of producing a greater maximal response than the endogenous agonist for the target receptor, and thus has an efficacy of more than 100%. Full agonists bind and activate a receptor, producing full efficacy at that receptor, one example of a drug that acts as a full agonist is isoproterenol, which mimics the action of adrenaline at β adrenoreceptors. Another example is morphine, which mimics the actions of endorphins at μ-opioid receptors throughout the nervous system. Partial agonists also bind and activate a receptor, but have only partial efficacy at the receptor relative to a full agonist. Agents like buprenorphine are used to treat opiate dependence for this reason, as they produce milder effects on the receptor with lower dependence. An inverse agonist is an agent that binds to the same receptor binding-site as an agonist for that receptor, inverse agonists exert the opposite pharmacological effect of a receptor agonist, not merely an absence of the agonist effect as seen with antagonist. An example is the inverse agonist rimonabant. A co-agonist works with other co-agonists to produce the desired effect together, NMDA receptor activation requires the binding of both glutamate, glycine and D-serine co-agonists. An irreversible agonist is a type of agonist that binds permanently to a receptor through the formation of covalent bonds, a few of these have been described. A selective agonist is selective for a type of receptor. E. g. buspirone is a selective agonist for serotonin 5-HT1A, terms that describe this phenomenon are functional selectivity, protean agonism, or selective receptor modulators. Potency is the amount of agonist needed to elicit a desired response, the potency of an agonist is inversely related to its EC50 value. The EC50 can be measured for a given agonist by determining the concentration of agonist needed to elicit half of the biological response of the agonist. The EC50 value is useful for comparing the potency of drugs with similar efficacies producing physiologically similar effects, the smaller the EC50 value, the greater the potency of the agonist, the lower the concentration of drug that is required to elicit the maximum biological response. This relationship, termed the index, is defined as the ratio TD50, ED50
28.
Gepirone
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Like other azapirones, it acts as a selective partial agonist of the 5-HT1A receptor. Gepirone was originally developed by Bristol-Myers Squibb, but was out-licensed to Fabre-Kramer in 1993, the U. S. Food and Drug Administration rejected approval for gepirone in 2004. It was submitted for the preregistration phase again in May 2007 after adding additional information from clinical trials as the FDA required in 2004, however, in 2007 it once again failed to convince the FDA of its qualities for treating anxiety and depression. In December 2015, the FDA once again gave gepirone a negative review for depression due to concerns of efficacy, unlike its relative buspirone, gepirone has negligible affinity for the D2 receptor, and its efficacy in activating the 5-HT1A is greater than that of buspirone. However, similarly to buspirone, gepirone metabolizes into 1-piperazine, which is known to act as an antagonist of the α2-adrenergic receptor
29.
Tandospirone
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Tandospirone, also known as metanopirone, is an anxiolytic and antidepressant drug used in China and Japan, where it is marketed by Dainippon Sumitomo Pharma. It is a member of the class of drugs and is closely related to other azapirones like buspirone and gepirone. Tandospirone is most commonly used as a treatment for anxiety and depressive disorders, such as generalised anxiety disorder, for both indications it usually takes a couple of weeks for therapeutic effects to be start being seen, although at higher doses more rapid anxiolytic responses have been seen. It has also used successfully as a treatment for bruxism. Tandospirone has also tried, successfully, as an adjunctive treatment for cognitive symptoms in schizophrenic individuals. Tandospirone acts as a potent and selective 5-HT1A receptor partial agonist, with a Ki affinity value of 27 ±5 nM, there is evidence of tandospirone having low but significant antagonistic activity at the α2-adrenergic receptor through its active metabolite 1-piperazine, however
30.
GABAA receptor
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The GABAA receptor is an ionotropic receptor and ligand-gated ion channel. Its endogenous ligand is γ-aminobutyric acid, the major inhibitory neurotransmitter in the nervous system. Upon activation, the GABAA receptor selectively conducts Cl− through its pore and this causes an inhibitory effect on neurotransmission by diminishing the chance of a successful action potential occurring. The reversal potential of the GABAA-mediated IPSP in normal solution is −70 mV, the active site of the GABAA receptor is the binding site for GABA and several drugs such as muscimol, gaboxadol, and bicuculline. The protein also contains a number of different allosteric binding sites which modulate the activity of the receptor indirectly, GABAA receptors occur in all organisms that have a nervous system. To a limited extent the receptors can be found in non-neuronal tissues, due to their wide distribution within the nervous system of mammals they play a role in virtually all brain functions. The ionotropic GABAA receptor protein complex is also the target of the benzodiazepine class of tranquilizer drugs. In addition peripheral benzodiazepine receptors exist which are not associated with GABAA receptors, in order for GABAA receptors to be sensitive to the action of benzodiazepines they need to contain an α and a γ subunit, between which the benzodiazepine binds. This potentiates the effect of the available GABA leading to sedative. Different benzodiazepines have different affinities for GABAA receptors made up of different collection of subunits, the much sought structure of GABAA receptor was finally resolved, with the disclosure of the crystal structure of human β3 homopentameric GABAA receptor. GABAA receptor is a transmembrane receptor that consists of five subunits arranged around a central pore. Each subunit comprises four transmembrane domains with both the N- and C-terminus located extracellularly, the receptor sits in the membrane of its neuron, usually localized at a synapse, postsynaptically. However, some isoforms may be found extrasynaptically, the net effect is typically inhibitory, reducing the activity of the neuron. The GABAA channel opens quickly and thus contributes to the part of the inhibitory post-synaptic potential. The endogenous ligand that binds to the site is inosine. There are numerous subunit isoforms for the GABAA receptor, which determine the receptors agonist affinity, chance of opening, conductance, five subunits can combine in different ways to form GABAA channels. The minimal requirement to produce a GABA-gated ion channel is the inclusion of both α and β subunits, but the most common type in the brain is a pentamer comprising two αs, two βs, and a γ. The receptor binds two GABA molecules, at the interface between an α and a β subunit, a number of ligands have been found to bind to various sites on the GABAA receptor complex and modulate it besides GABA itself
. PMID 8380639.