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).
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.
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.
The serotonin 1A receptor is a subtype of serotonin receptor, or 5-HT receptor, 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 hyperpolarisation 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 be discovered.
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.
LY-341495 is a research drug developed by the pharmaceutical company Eli Lilly, which acts as a potent and selective orthosteric antagonist for the group II metabotropic glutamate receptors (mGluR2/3).
EMD-386088 is an indole derivative which is used in scientific research. It acts as a potent 5-HT6 receptor partial agonist, with a Ki of 1 nM, a significantly higher affinity than older 5-HT6 agonists such as EMDT, although it possesses moderate affinity for the 5-HT3 receptor as well. Subsequent research has determined that EMD-386088 is also a dopamine reuptake inhibitor and that this action is involved in the antidepressant-like effects of the drug in rodents.
AS-19 is a substance which acts as a potent agonist at the 5HT7 receptor, with an IC50 of 0.83nM. It reverses the amnesia induced by drugs such as scopolamine and dizocilpine and improves long-term memory acquisition, but inhibits short-term memory formation.
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.
SB-269970 is a drug and research chemical developed by GlaxoSmithKline used in scientific studies. It is believed to act as a selective 5-HT7 receptor antagonist (EC50 = 1.25 nM) (or possibly inverse agonist). A subsequent study in guinea pig at 10 uM showed that it also blocks the α2-adrenergic receptor activity. The significant difference in test concentrations, however, confirms the selectivity of SB-269970 for the 5-HT7 receptor.
A serotonin releasing agent (SRA) is a type of drug that induces the release of serotonin into the neuronal synaptic cleft. A selective serotonin releasing agent (SSRA) is an SRA with less significant or no efficacy in producing neurotransmitter efflux at other types of monoamine neurons.
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.
Roxindole (EMD-49,980) is a dopaminergic and serotonergic drug which was originally developed by Merck KGaA for the treatment of schizophrenia. In clinical trials its antipsychotic efficacy was only modest but it was unexpectedly found to produce potent and rapid antidepressant and anxiolytic effects. As a result, roxindole was further researched for the treatment of depression instead. It has also been investigated as a therapy for Parkinson's disease and prolactinoma.
WAY-181187 is a high affinity and selective 5-HT6 receptor full agonist. It induces robust increases in extracellular GABA levels in the frontal cortex, hippocampus, striatum, and amygdala of rats without affecting concentrations in the nucleus accumbens or thalamus, and has modest to no effects on norepinephrine, serotonin, dopamine, or glutamate levels in these areas. WAY-181187 has demonstrated preclinical efficacy in rodent models of depression, anxiety, and notably obsessive-compulsive disorder, though it has also been shown to impair cognition and memory.
Pruvanserin is a selective 5-HT2A receptor antagonist which was under development by Eli Lilly and Company for the treatment of insomnia. It was in phase II clinical trials in 2008 but appears to have been discontinued as it is no longer in the company's development pipeline. In addition to its sleep-improving properties, pruvanserin has also been shown to have antidepressant, anxiolytic, and working memory-enhancing effects in animal studies.
ST-1936 (2-methyl-5-chloro-N,N-dimethyltryptamine) is a tryptamine derivative which is used in scientific research. It acts as a selective 5-HT6 receptor agonist, with a Ki of 13 nM, and much weaker action at 5-HT2B and 5-HT7 subtypes. In animal studies it has been found to increase dopamine and noradrenaline mediated signalling but decreases glutamatergic transmission, and has antidepressant effects.
SB-243213 is a research chemical which acts as a selective inverse agonist for the 5HT2C receptor and has anxiolytic effects. It has better than 100x selectivity for 5-HT2C over all other receptor subtypes tested, and a longer duration of action compared to older 5-HT2C antagonist ligands.
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