5-HT receptors, 5-hydroxytryptamine receptors, or serotonin receptors, are a group of G protein-coupled receptor and ligand-gated ion channels found in the central and peripheral nervous systems. They mediate both excitatory and inhibitory neurotransmission. The serotonin receptors are activated by the neurotransmitter serotonin, which acts as their natural ligand.
Azapirones are a class of drugs used as anxiolytics, antidepressants, and antipsychotics. They are commonly used as add-ons to other antidepressants, such as selective serotonin reuptake inhibitors (SSRIs).
Buspirone, sold under the brand name Buspar, among others, is an anxiolytic, a medication primarily used to treat anxiety disorders, particularly generalized anxiety disorder. It is a serotonin 5-HT1A receptor agonist, increasing action at serotonin receptors in the brain. It is taken orally, and takes two to six weeks to be fully effective.
A serotonin receptor agonist is an agonist of one or more serotonin receptors. They activate serotonin receptors in a manner similar to that of serotonin, a neurotransmitter and hormone and the endogenous ligand of the serotonin receptors.
Tandospirone, sold under the brand name Sediel, is an anxiolytic and antidepressant medication used in Japan and China, where it is marketed by Dainippon Sumitomo Pharma. It is a member of the azapirone class of drugs and is closely related to other azapirones like buspirone and gepirone.
The serotonin 1A receptor is a subtype of serotonin receptors, or 5-HT receptors, that binds serotonin, also known as 5-HT, a neurotransmitter. 5-HT1A is expressed in the brain, spleen, and neonatal kidney. It is a G protein-coupled receptor (GPCR), coupled to the Gi protein, and its activation in the brain mediates hyperpolarization and reduction of firing rate of the postsynaptic neuron. In humans, the serotonin 1A receptor is encoded by the HTR1A gene.
8-OH-DPAT is a research chemical of the aminotetralin chemical class which was developed in the 1980s and has been widely used to study the function of the 5-HT1A receptor. It was one of the first major 5-HT1A receptor full agonists to have been discovered.
Binospirone (MDL-73,005-EF) is a drug which acts as a partial agonist at 5-HT1A somatodendritic autoreceptors but as an antagonist at postsynaptic 5-HT1A receptors. It has anxiolytic effects.
Zalospirone (WY-47,846) is a selective 5-HT1A partial agonist of the azapirone chemical class. It was found to be effective in the treatment of anxiety and depression in clinical trials, but a high proportion of subjects dropped out due to side effects and development was subsequently never completed.
U-92,016-A is a psychoactive drug and research chemical used in scientific studies. It acts as a potent, high efficacy, and selective 5-HT1A receptor full agonist with a long duration of action. It has been suggested that it could be developed as an anxiolytic or antidepressant drug.
Naluzotan is a serotonergic drug of the phenylpiperazine class that was under investigation by EPIX Pharmaceuticals Inc for the treatment of generalized anxiety disorder and major depressive disorder. It acts as a selective and potent 5-HT1A receptor partial agonist, readily stimulating prolactin responses, though it has also been found to bind to and activate the σ receptor. Naluzotan was well tolerated in clinical trials, with more patients in the control group dropping out due to adverse effects than in the active group in one study. The most frequently reported side effect was headache in 15% of patients. In addition, naluzotan demonstrated significant antidepressant and anxiolytic effects as per the HAM-D and MADRS and the HAM-A, respectively, in some trials, but in others it did not. In the end it was not found to be significantly superior enough to placebo and development was stopped.
Alnespirone (S-20,499) is a selective 5-HT1A receptor full agonist of the azapirone chemical class. It has antidepressant and anxiolytic effects.
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.
Enilospirone (CERM-3,726) is a selective 5-HT1A receptor agonist of the azapirone class.
Revospirone is an azapirone drug which was patented as a veterinary tranquilizer but was never marketed. It acts as a selective 5-HT1A receptor partial agonist. Similarly to other azapirones such as buspirone, revospirone produces 1-(2-pyrimidinyl)piperazine (1-PP) as an active metabolite. As a result, it also acts as an α2-adrenergic receptor antagonist to an extent.
Umespirone (KC-9172) is a drug of the azapirone class which possesses anxiolytic and antipsychotic properties. It behaves as a 5-HT1A receptor partial agonist (Ki = 15 nM), D2 receptor partial agonist (Ki = 23 nM), and α1-adrenoceptor receptor antagonist (Ki = 14 nM), and also has weak affinity for the sigma receptor (Ki = 558 nM). Unlike many other anxiolytics and antipsychotics, umespirone produces minimal sedation, cognitive/memory impairment, catalepsy, and extrapyramidal symptoms.
Lesopitron (E-4424) is a selective full agonist of the 5-HT1A receptor which is structurally related to the azapirones. In 2001 it was under development by Esteve as an anxiolytic for the treatment of generalized anxiety disorder (GAD). It made it to phase II clinical trials but was apparently discontinued as no new information on lesopitron has surfaced since.
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 naphthylpiperazine 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.
