The 5HT6 receptor is a subtype of 5HT receptor that binds the endogenous neurotransmitter serotonin (5-hydroxytryptamine, 5HT). It is a G protein-coupled receptor (GPCR) that is coupled to Gs and mediates excitatory neurotransmission. HTR6 denotes the human gene encoding for the receptor.
The 5-HT7 receptor is a member of the GPCR superfamily of cell surface receptors and is activated by the neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) The 5-HT7 receptor is coupled to Gs (stimulates the production of the intracellular signaling molecule cAMP) and is expressed in a variety of human tissues, particularly in the brain, the gastrointestinal tract, and in various blood vessels. 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.
MS-245 is a tryptamine derivative used in scientific research. It acts as a selective 5-HT6 receptor antagonist with a Ki of 2.3 nM, and was derived through structure-activity relationship development of the selective 5-HT6 agonist EMDT. It has been used as a lead compound for further development of tryptamine-derived 5-HT6 antagonists. In animal studies it has been shown to boost the activity of, but not substitute for, both amphetamine and nicotine.
AL-34662 is an indazole derivative drug that is being developed for the treatment of glaucoma. It acts as a selective 5-HT2A receptor agonist, the same target as that of psychedelic drugs like psilocin, but unlike these drugs, AL-34662 was designed specifically as a peripherally selective drug, which does not cross the blood–brain barrier. This means that AL-34662 can exploit a useful side effect of the hallucinogenic 5-HT2A agonists, namely reduction in intra-ocular pressure and hence relief from the symptoms of glaucoma, but without causing the hallucinogenic effects that make centrally active 5-HT2A agonists unsuitable for clinical use. In animal studies, AL-34662 has been shown to be potent and effective in the treatment of symptoms of glaucoma, with minimal side effects.
YM-348 is an indazole derivative drug which acts as a potent and selective 5-HT2C receptor agonist, with an EC50 of 1nM and 15x selectivity over 5-HT2A, although it only has moderate selectivity of 3x over the closely related 5-HT2B receptor. It has thermogenic and anorectic effects in animal studies, making it potentially useful for the treatment of obesity.
AL-37350A (4,5-DHP-AMT) is a tryptamine derivative which acts as a potent and selective agonist for the serotonin receptor 5-HT2A, with a Ki of 2.0 nM, and moderate selectivity over the related 5-HT2B and 5-HT2C receptors. It has been shown to have ocular hypotensive activity in animal models, suggesting it may be useful for the treatment of glaucoma.
5-Fluoro-N,N-dimethyltryptamine is a tryptamine derivative related to compounds such as 5-bromo-DMT and 5-MeO-DMT. Fluorination of psychedelic tryptamines either reduces or has little effect on 5-HT2A/C receptor affinity or intrinsic activity, although 6-fluoro-DET is inactive as a psychedelic despite acting as a 5-HT2A agonist, while 4-fluoro-5-methoxy-DMT is a much stronger agonist at 5-HT1A than 5-HT2A.
Dimemebfe (5-MeO-BFE) is a recreational drug and research chemical. It acts as an agonist for the 5-HT1A and 5-HT2 family of serotonin receptors. It is related in structure to the psychedelic tryptamine derivative 5-MeO-DMT, but with the indole nitrogen replaced by oxygen, making dimemebfe a benzofuran derivative. It is several times less potent as a serotonin agonist than 5-MeO-DMT and with relatively more activity at 5-HT1A, but still shows strongest effects at the 5-HT2 family of receptors.
5-Methoxy-7,N,N-trimethyltryptamine (5-MeO-7,N,N-TMT, 5-MeO-7-TMT), is a tryptamine derivative which acts as an agonist at the 5-HT2 serotonin receptors. In animal tests, both 7,N,N-TMT and 5-MeO-7,N,N-TMT produced behavioural responses similar to those of psychedelic drugs such as DMT and 5-MeO-DMT, but compounds with larger 7-position substituents such as 7-ethyl-DMT and 7-bromo-DMT did not produce psychedelic-appropriate responding despite high 5-HT2 receptor binding affinity, suggesting these may be antagonists or weak partial agonists for the 5-HT2 receptors. The related compound 7-MeO-MiPT (cf. 5-MeO-MiPT) was also found to be inactive, suggesting that the 7-position has poor tolerance for bulky groups at this position, at least if agonist activity is desired.
7,N,N-trimethyltryptamine (7-methyl-DMT, 7-TMT), is a tryptamine derivative which acts as an agonist of 5-HT2 receptors. In animal tests, both 7-TMT and its 5-methoxy derivative 5-MeO-7-TMT produced behavioural responses similar to those of psychedelic drugs such as DMT, but the larger 7-ethyl and 7-bromo derivatives of DMT did not produce psychedelic responses despite having higher 5-HT2 receptor affinity in vitro (cf. DOBU, DOAM). 7-TMT also weakly inhibits reuptake of serotonin but with little effect on dopamine or noradrenaline reuptake.
4-Fluoro-5-Methoxy-N,N-dimethyltryptamine (4-F-5-MeO-DMT) was first described by David E. Nichols team in 2000. It is a potent 5-HT1A agonist. Substitution with the 4-fluorine markedly increased 5-HT1A selectivity over 5-HT2A/2C receptors with potency greater than that of the 5-HT1A agonist 8-OH-DPAT.
CP-93129 is a drug which acts as a potent and selective serotonin 5-HT1B receptor agonist, with approximately 150x and 200x selectivity over the closely related 5-HT1D and 5-HT1A receptors. It is used in the study of 5-HT1B receptors in the brain, particularly their role in modulating the release of other neurotransmitters.
Nelotanserin is a drug developed by Arena Pharmaceuticals which acts as an inverse agonist on the serotonin receptor subtype 5-HT2A and was under development for the treatment of insomnia. It was shown to be effective and well tolerated in clinical trials, but development was halted in December 2008 because the substance did not meet the trial's effectiveness endpoints. Research continues on newer analogues which may potentially be more successful. More recently, nelotanserin has been repurposed for the treatment of Lewy body disease. As of 2017, it is in phase II clinical trials for this indication.
5-Ethyl-N,N-dimethyltryptamine is a tryptamine derivative which acts as an agonist at the 5-HT1A and 5-HT1D serotonin receptors, with around 3x selectivity for 5-HT1D.
5-(Nonyloxy)tryptamine is a tryptamine derivative which acts as a selective agonist at the 5-HT1B receptor. Increasing the O-alkoxy chain length in this series gives generally increasing potency and selectivity for 5-HT1B, with highest activity found for the nonyloxy derivative, having a 5-HT1B binding affinity of 1.0 nM, and around 300-fold selectivity over the related 5-HT1A receptor.
SB-206553 is a drug which acts as a mixed antagonist for the 5-HT2B and 5-HT2C serotonin receptors. It has anxiolytic properties in animal studies and interacts with a range of other drugs. It has also been shown to act as a positive allosteric modulator of α7 nicotinic acetylcholine receptors. Modified derivatives of SB-206553 have been used to probe the structure of the 5-HT2B receptor.
Substituted tryptamines, or serotonin analogues, are organic compounds which may be thought of as being derived from tryptamine itself. The molecular structures of all tryptamines contain an indole ring, joined to an amino (NH2) group via an ethyl (−CH2–CH2−) sidechain. In substituted tryptamines, the indole ring, sidechain, and/or amino group are modified by substituting another group for one of the hydrogen (H) atoms.
CP-132,484 is a tryptamine derivative which acts as a potent and selective agonist for the 5-HT2 family of serotonin receptors. It has reasonable selectivity for 5-HT2A and 5-HT2C subtypes over 5-HT2B, but is only slightly selective for 5-HT2A over 5-HT2C. This compound and several related analogues have been shown to have ocular hypotensive activity in animal models, suggesting they may be useful for the treatment of glaucoma.
5-MeO-DiBF is a psychedelic that has been sold online as a designer drug and was first definitively identified in December 2015 by a forensic laboratory in Slovenia. It is thought to act as an agonist for the 5-HT1A and 5-HT2 family of serotonin receptors. It is related in structure to the psychedelic tryptamine derivative 5-MeO-DiPT, but with the indole nitrogen replaced by oxygen, making 5-MeO-DiBF a benzofuran derivative. It is several times less potent as a serotonin agonist than 5-MeO-DiPT and with relatively more activity at 5-HT1A, but still shows strongest effects at the 5-HT2 family of receptors.
SN-22 is a chemical compound which acts as a moderately selective agonist at the 5-HT2 family of serotonin receptors, with a Ki of 19nM at 5HT2 subtypes vs 514 nM at 5-HT1A receptors. Many related derivatives are known, most of which are ligands for 5-HT1A, 5-HT6 or dopamine D2 receptors or show SSRI activity.
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