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.
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).
Functional selectivity is the ligand-dependent selectivity for certain signal transduction pathways relative to a reference ligand at the same receptor. Functional selectivity can be present when a receptor has several possible signal transduction pathways. To which degree each pathway is activated thus depends on which ligand binds to the receptor. Functional selectivity, or biased signaling, is most extensively characterized at G protein coupled receptors (GPCRs). A number of biased agonists, such as those at muscarinic M2 receptors tested as analgesics or antiproliferative drugs, or those at opioid receptors that mediate pain, show potential at various receptor families to increase beneficial properties while reducing side effects. For example, pre-clinical studies with G protein biased agonists at the μ-opioid receptor show equivalent efficacy for treating pain with reduced risk for addictive potential and respiratory depression. Studies within the chemokine receptor system also suggest that GPCR biased agonism is physiologically relevant. For example, a beta-arrestin biased agonist of the chemokine receptor CXCR3 induced greater chemotaxis of T cells relative to a G protein biased agonist.
Lisuride, sold under the brand name Dopergin among others, is a monoaminergic medication of the ergoline class which is used in the treatment of Parkinson's disease, migraine, and high prolactin levels. It is taken by mouth.
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.
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.
Dopamine receptor D2, also known as D2R, is a protein that, in humans, is encoded by the DRD2 gene. After work from Paul Greengard's lab had suggested that dopamine receptors were the site of action of antipsychotic drugs, several groups, including those of Solomon Snyder and Philip Seeman used a radiolabeled antipsychotic drug to identify what is now known as the dopamine D2 receptor. The dopamine D2 receptor is the main receptor for most antipsychotic drugs. The structure of DRD2 in complex with the atypical antipsychotic risperidone has been determined.
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.
SKF-81,297 is a synthetic drug of the benzazepine chemical class that acts as a selective dopamine D1/D5 receptor full agonist, and produces a characteristic stimulant-like pattern of anorexia, hyperactivity and self-administration in animals. This profile is shared with several related drugs such as 6-Br-APB and SKF-82,958, but not with certain other D1 full agonists such as A-77,636, reflecting functional selectivity of D1 activation. Newer findings reveal that SKF-81,297 additionally acts as a partial agonist at D1-D2 receptor heteromers.
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.
Vabicaserin was a novel antipsychotic and anorectic under development by Wyeth. As of 2010 it is no longer in clinical trials for the treatment of psychosis. It was also under investigation as an antidepressant but this indication appears to have been dropped as well.
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.
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.
WAY-161503 is a full agonist of 5-HT2C receptors (Ki = 3.3 nM for displacement of DOI), ~6-fold less potent at 5-HT2A receptors (Ki = 18 nM) and 20-fold less potent at 5-HT2B receptors (Ki = 60 nM). In functional studies, it stimulates calcium mobilization coupled to 5-HT2C, 5-HT2B, and 5-HT2A receptors with EC50 values of 0.8, 1.8, and 7 nM, respectively. WAY-161503 has been reported to produce dose-dependent decreases in food intake in 24-hour fasted normal Sprague-Dawley rats, diet-induced obese mice, and obese Zucker rats with ED50 values of 1.9, 6.8, and 0.73 mg/kg, respectively.
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.
The 25-NB (25x-NBx) series, sometimes alternatively referred to as the NBOMe compounds, is a family of serotonergic psychedelics. They are substituted phenethylamines and were derived from the 2C family. They act as selective agonists of the serotonin 5-HT2A receptor. The 25-NB family is unique relative to other classes of psychedelics in that they are, generally speaking, extremely potent and relatively selective for the 5-HT2A receptor. Use of NBOMe series drugs has caused many deaths and hospitalisations since the drugs popularisation in the 2010s. This is primarily due to their high potency, unpredictable pharmacokinetics, and sellers passing off the compounds in the series as LSD.
25N-NBPh (NBPh-2C-N) is a phenethylamine derivative from the 25-NB class, which acts as a potent agonist at the 5-HT2A receptor with weaker activity at 5-HT2B and 5-HT2C. 25N-NBPh is a biased agonist, producing robust activation of 5-HT2A coupled signalling pathways mediated by beta arrestin 2, but with only slight activation of pathways mediated via Gq. In animal studies it produces a modest head-twitch response when administered by itself, but blocks the effects of the fully active psychedelic DOI.
25N-N1-Nap is a phenethylamine derivative from the 25-NB class, which acts as a potent agonist at the 5-HT2A receptor with weaker activity at 5-HT2B and 5-HT2C. 25N-N1-Nap is a biased agonist, producing robust activation of 5-HT2A coupled signalling pathways mediated by beta arrestin 2, but with little or no activation of pathways mediated via Gq. In animal studies it produces antipsychotic effects but without producing the head-twitch response associated with psychedelic activity.
