An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the agonist, while an inverse agonist causes an action opposite to that of the agonist.
The 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 (GPCR). The 5-HT2A receptor is a cell surface receptor, but has several intracellular locations.
Naftidrofuryl (INN), also known as nafronyl or as the oxalate salt naftidrofuryl oxalate or nafronyl oxalate, is a vasodilator used in the management of peripheral and cerebral vascular disorders. It is also claimed to enhance cellular oxidative capacity. The drug act as a selective antagonist of 5-HT2 receptors (with action as an inverse agonist of the 5-HT2A receptor specifically characterized). Naftidrofuryl is also licensed for the treatment of intermittent claudication due to peripheral arterial disease.
5-Hydroxytryptamine receptor 2B (5-HT2B) 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 (5-hydroxytryptamine, 5-HT). Like all 5-HT2 receptors, the 5-HT2B receptor is Gq/G11-protein coupled, leading to downstream activation of phospholipase C.
5-Carboxamidotryptamine (5-CT) is a tryptamine derivative closely related to the neurotransmitter serotonin.
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.
Ro60-0175 is a drug developed by Hoffmann–La Roche, which has applications in scientific research. It acts as a potent and selective agonist for both the 5-HT2B and 5-HT2C serotonin receptor subtypes, with good selectivity over the closely related 5-HT2A subtype, and little or no affinity at other receptors.
AL-37350A (4,5-DHP-AMT) is a tricyclic 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.
PNU-22394 is a drug which acts as an agonist at serotonin 5-HT2 receptors, with strongest binding affinity for 5-HT2A and 5-HT2C and slightly weaker at 5-HT2B, although it is only a full agonist at 5-HT2C, but partial agonist at 5-HT2A and 5-HT2B. It has anorectic effects in both animal studies and human trials, along with "Pro-Cognitive Properties", although it has never been developed for medical use.
ORG-37684 is a drug developed by Organon, which acts as a potent and selective agonist for the 5-HT2 receptor family, with highest affinity at 5-HT2C and lowest at 5-HT2B subtypes. It has anorectic effects in animal studies and has been researched as a potential weight loss drug for use in humans.
CGS-12066A is a drug which acts as a potent and selective agonist for the 5-HT1B receptor with lower affinity for the three 5-HT2 receptor subtypes. It is used for studying the role of the 5-HT1B receptor in various processes including perception of pain and the sleep-wake cycle.
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.
VER-3323 is a drug which acts as a selective agonist for both the 5-HT2B and 5-HT2C serotonin receptor subtypes, with moderate selectivity for 5-HT2C, but relatively low affinity for 5-HT2A. It has potent anorectic effects in animal studies.
ORG-12962 is a pyridinylpiperazine drug developed by Organon, which acts as a potent and selective agonist for the 5-HT2 receptor family, with highest affinity at 5-HT2C and lowest at 5-HT2B subtypes. It was developed as a potential anti-anxiety drug, but was discontinued from human trials after tests in a public speaking challenge showed that its anti-anxiety effects were accompanied by side effects such as dizziness and a "spacey" feeling, which were attributed to poor selectivity in vivo over the hallucinogenic 5-HT2A receptor.
1-(2-Dimethylaminoethyl)dihydropyrano(3,2-e)indole (4,5-DHP-DMT) is a tricyclic tryptamine derivative which acts as a potent and reasonably selective partial agonist for the serotonin receptor 5-HT2A, with a Ki of 17.0 nM, and moderate selectivity over related serotonin receptors. It has lower 5-HT2 affinity and efficacy than the related compound AL-37350A, but higher lipophilicity.
5-HT2C receptor agonists are a class of drugs that activate 5-HT2C receptors. They have been investigated for the treatment of a number of conditions including obesity, psychiatric disorders, sexual dysfunction and urinary incontinence.
25CN-NBOH is a compound indirectly derived from the phenethylamine series of hallucinogens, which was discovered in 2014 at the University of Copenhagen. This compound is notable as one of the most selective agonist ligands for the 5-HT2A receptor yet discovered, with a pKi of 8.88 at the human 5-HT2A receptor and with 100x selectivity for 5-HT2A over 5-HT2C, and 46x selectivity for 5-HT2A over 5-HT2B. A tritiated version of 25CN-NBOH has also been accessed and used for more detailed investigations of the binding to 5-HT2 receptors and autoradiography.
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.
CPD-1 (LS-193743) is a drug with a benzofuranyl piperazine structure, which acts as a potent and selective agonist for the 5-HT2 receptor family, with highest affinity and full agonist efficacy at the 5-HT2C subtype, and lower affinity and partial agonist action at the 5-HT2A and 5-HT2B subtypes.
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