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.
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. 5-HT is short for 5-hydroxy-tryptamine or 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.
5-Hydroxytryptamine receptor 4 is a protein that in humans is encoded by the HTR4 gene.
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.
5-hydroxytryptamine receptor 1B also known as the 5-HT1B receptor is a protein that in humans is encoded by the HTR1B gene. The 5-HT1B receptor is a 5-HT receptor subtype.
5-hydroxytryptamine (serotonin) 1E receptor (5-HT1E) is a highly expressed human G-protein coupled receptor that belongs to the 5-HT1 receptor family. The human gene is denoted as HTR1E.
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).
5-Hydroxytryptamine (serotonin) receptor 5A, also known as HTR5A, is a protein that in humans is encoded by the HTR5A gene. Agonists and antagonists for 5-HT receptors, as well as serotonin uptake inhibitors, present promnesic (memory-promoting) and/or anti-amnesic effects under different conditions, and 5-HT receptors are also associated with neural changes.
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.
TCB-2 is a hallucinogen discovered in 2006 by Thomas McLean working in the lab of David Nichols at Purdue University. It is a conformationally-restricted derivative of the phenethylamine 2C-B, also a hallucinogen, and acts as a potent agonist for the 5-HT2A and 5-HT2C receptors with a Ki of 0.26 nM at the human 5-HT2A receptor. In drug-substitution experiments in rats, TCB-2 was found to be of similar potency to both LSD and Bromo-DragonFLY, ranking it among the most potent phenethylamine hallucinogens yet discovered. This high potency and selectivity has made TCB-2 useful for distinguishing 5-HT2A mediated responses from those produced by other similar receptors. TCB-2 has similar but not identical effects in animals to related phenethylamine hallucinogens such as DOI, and has been used for studying how the function of the 5-HT2A receptor differs from that of other serotonin receptors in a number of animal models, such as studies of cocaine addiction and neuropathic pain.
2-Ethyl-5-methoxy-N,N-dimethyltryptamine (EMDT) is a tryptamine derivative which is used in scientific research. It acts as a selective 5-HT6 receptor agonist, with a Ki of 16 nM, and was one of the first selective agonists developed for this receptor. EMDT inhibits both short- and long-term memory formation in animal studies, and this effect can be reversed by the selective 5-HT6 antagonist SB-399,885. Additionally, it is active in the tail suspension test, suggesting that it could be an effective antidepressant.
CP-94253 is a drug which acts as a potent and selective serotonin 5-HT1B receptor agonist, with approximately 25x and 40x selectivity over the closely related 5-HT1D and 5-HT1A receptors. It has a range of behavioral effects, based on animal testing. The effects include the following: promoting wakefulness by increasing dopamine release in the brain; reducing food intake and promoting satiety; enhancing the reinforcing effects of cocaine; and possible antidepressant effects.A recent study found that "Regardless of sex, CP94253 decreased cocaine intake after abstinence and during resumption of SA [self-administration] and decreased cue reactivity" suggesting that agonism of the inhibitory 5-HT2B receptors may diminish the cognitive reward of cocaine usage and increased use of the drug without a period of abstinence may be a product of test subjects trying to achieve a previously rewarding experience through larger dosages of cocaine.
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 a concentration of 10 μM showed that it also blocks the α2-adrenergic receptor. The large difference in test concentrations however confirms the selectivity of SB-269970 for the 5-HT7 receptor.
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.
Capeserod (INN; development code SL65.0155) is a selective 5-HT4 receptor partial agonist with Ki = 0.6 nM and IA = 40–50% (relative to serotonin). It potently enhances cognition, learning, and memory, and also possesses antidepressant effects. Capeserod was in phase II clinical trials around 2004–2006 for the treatment of memory deficits and dementia but no new information has surfaced since and it appears to have been abandoned.
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.
E-55888 is a drug developed by Esteve, which acts as a potent and selective full agonist at the 5HT7 serotonin receptor, and is used for investigating the role of 5-HT7 receptors in the perception of pain. When administered by itself, E-55888 is anti-hyperalgesic but not analgesic, but when administered alongside morphine, E-55888 was found to significantly increase the analgesic effects.
LP-211 is a drug which acts as a potent and selective agonist at the 5HT7 serotonin receptor, with better brain penetration than older 5-HT7 agonists in the same series, and similar effects in animals.
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