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. 5-HT is short for 5-hydroxy-tryptamine, which is serotonin. This is the main excitatory receptor subtype among the GPCRs for serotonin, although 5-HT2A may also have an inhibitory effect on certain areas such as the visual cortex and the orbitofrontal cortex. This receptor was first noted for its importance as a target of serotonergic psychedelic drugs such as LSD and psilocybin mushrooms. 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.
Flesinoxan (DU-29,373) is a potent and selective 5-HT1A receptor partial/near-full agonist of the phenylpiperazine class. Originally developed as a potential antihypertensive drug, flesinoxan was later found to possess antidepressant and anxiolytic effects in animal tests. As a result, it was investigated in several small human pilot studies for the treatment of major depressive disorder, and was found to have robust effectiveness and very good tolerability. However, due to "management decisions", the development of flesinoxan was stopped and it was not pursued any further.
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.
WAY-100135 is a serotonergic drug of the phenylpiperazine family which is used in scientific research. It acts as potent 5-HT1A receptor antagonist, and was originally believed to be highly selective, but further studies have demonstrated that it also acts as a partial agonist of the 5-HT1D receptor (pKi = 7.58; virtually the same affinity for 5-HT1A), and to a much lesser extent, of the 5-HT1B receptor (pKi = 5.82). These findings may have prompted the development of the related compound WAY-100635, another purportedly selective and even more potent 5-HT1A antagonist, which was synthesized shortly thereafter. However, WAY-100635 turned out to be non-selective as well, having been shown to act additionally as a potent D4 receptor agonist later on.
RU-24,969 is a drug and research chemical widely used in scientific studies. It is a selective agonist at the 5-HT1A and 5-HT1B receptors, with preference for the latter. As with other 5-HT1B agonists such as CP-94,253, RU-24,969 has been found to increase the reinforcing properties of cocaine, suggesting a role for 5-HT1B receptors in cocaine addiction.
S-15535 is a phenylpiperazine drug which is a potent and highly selective 5-HT1A receptor ligand that acts as an agonist and antagonist at the presynaptic and postsynaptic 5-HT1A receptors, respectively. It has anxiolytic properties.
Eptapirone (F-11,440) is a very potent and highly selective 5-HT1A receptor full agonist of the azapirone family. Its affinity for the 5-HT1A receptor was reported to be 4.8 nM (Ki), and its intrinsic activity approximately equal to that of serotonin.
F-15,599, also known as NLX-101, is a potent and selective 5-HT1A receptor full agonist. It displays functional selectivity by strongly activating 5-HT1A receptors in the postsynaptic prefrontal cortex while having little effect on somatodendritic autoreceptors in the raphe nucleus. As a result, it has been touted as a preferential postsynaptic 5-HT1A receptor agonist and has been investigated as a novel potential antidepressant.
Osemozotan (MKC-242) is a selective 5-HT1A receptor agonist with some functional selectivity, acting as a full agonist at presynaptic and a partial agonist at postsynaptic 5-HT1A receptors. 5-HT1A receptor stimulation influences the release of various neurotransmitters including serotonin, dopamine, norepinephrine, and acetylcholine. 5-HT1A receptors are inhibitory G protein-coupled receptor. Osemozotan has antidepressant, anxiolytic, antiobsessional, serenic, and analgesic effects in animal studies, and is used to investigate the role of 5-HT1A receptors in modulating the release of dopamine and serotonin in the brain, and their involvement in addiction to abused stimulants such as cocaine and methamphetamine.
CSP-2503 is a potent and selective 5-HT1A receptor agonist, 5-HT2A receptor antagonist, and 5-HT3 receptor antagonist of the phenylpiperazine class. First synthesized in 2003, it was designed based on computational models and QSAR studies. In rat studies, CSP-2503 has demonstrated anxiolytic effects, and thus has been suggested as a treatment for anxiety in humans with a multimodal mechanism of action.
Ro60-0213 is a drug developed by Hoffmann–La Roche, which acts as a potent and selective agonist for the 5-HT2C serotonin receptor, with more than 100x selectivity over other closely related serotonin receptor subtypes, and little or no affinity at other receptors. It was developed as a potential antidepressant, but was discontinued from clinical development at an early stage due to toxicity concerns. However the high selectivity of Ro60-0213 for 5-HT2C makes it of continued interest for research into serotonin receptors.
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.
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-MeO-NBpBrT is a N-substituted member of the methoxytryptamine family of compounds. Like other such compounds it acts as an antagonist for the 5-HT2A receptor, with a claimed 100x selectivity over the closely related 5-HT2C receptor. While N-benzyl substitution of psychedelic phenethylamines often results in potent 5-HT2A agonists, it had been thought that N-benzyl tryptamines show much lower efficacy and are either very weak partial agonists or antagonists at 5-HT2A, though more recent research has shown stronger agonist activity for 3-substituted benzyl derivatives. Extending the benzyl group to a substituted phenethyl can also recover agonist activity in certain cases.
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.
DOB-FLY is a recreational designer drug with psychedelic effects. It can be regarded as the alpha-methyl derivative of 2C-B-FLY or the partially saturated counterpart of bromo-dragonfly. Unlike bromo-dragonfly, DOB-FLY is only slightly more potent than DOB itself, with an active dose in humans of around 1 mg.
Omidenepag isopropyl is a pharmaceutical drug used for the treatment of glaucoma and ocular hypertension.
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