Human vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the AVP gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It then travels down the axon terminating in the posterior pituitary, and is released from vesicles into the circulation in response to extracellular fluid hypertonicity (hyperosmolality). AVP has two primary functions. First, it increases the amount of solute-free water reabsorbed back into the circulation from the filtrate in the kidney tubules of the nephrons. Second, AVP constricts arterioles, which increases peripheral vascular resistance and raises arterial blood pressure.
Oxytocin is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. Present in animals since early stages of evolution, in humans it plays roles in behavior that include social bonding, love, reproduction, childbirth, and the period after childbirth. Oxytocin is released into the bloodstream as a hormone in response to sexual activity and during childbirth. It is also available in pharmaceutical form. In either form, oxytocin stimulates uterine contractions to speed up the process of childbirth. In its natural form, it also plays a role in maternal bonding and milk production. Production and secretion of oxytocin is controlled by a positive feedback mechanism, where its initial release stimulates production and release of further oxytocin. For example, when oxytocin is released during a contraction of the uterus at the start of childbirth, this stimulates production and release of more oxytocin and an increase in the intensity and frequency of contractions. This process compounds in intensity and frequency and continues until the triggering activity ceases. A similar process takes place during lactation and during sexual activity.
Empathogens or entactogens are a class of psychoactive drugs that induce the production of experiences of emotional communion, oneness, relatedness, emotional openness—that is, empathy or sympathy—as particularly observed and reported for experiences with 3,4-methylenedioxymethamphetamine (MDMA). This class of drug is distinguished from the classes of hallucinogen or psychedelic, and amphetamine or stimulants. Major members of this class include MDMA, MDA, MDEA, MDOH, MBDB, 5-APB, 5-MAPB, 6-APB, 6-MAPB, methylone, mephedrone, GHB, αMT, and αET, MDAI among others. Most entactogens are phenethylamines and amphetamines, although several, such as αMT and αET, are tryptamines. When referring to MDMA and its counterparts, the term MDxx is often used. Entactogens are sometimes incorrectly referred to as hallucinogens or stimulants, although many entactogens such as ecstasy exhibit psychedelic or stimulant properties as well.
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.
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.
In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. The etymology stems from Latin ligare, which means 'to bind'. In protein-ligand binding, the ligand is usually a molecule which produces a signal by binding to a site on a target protein. The binding typically results in a change of conformational isomerism (conformation) of the target protein. In DNA-ligand binding studies, the ligand can be a small molecule, ion, or protein which binds to the DNA double helix. The relationship between ligand and binding partner is a function of charge, hydrophobicity, and molecular structure.
Neurotensin receptors are transmembrane receptors that bind the neurotransmitter neurotensin. Two of the receptors encoded by the NTSR1 and NTSR2 genes contain seven transmembrane helices and are G protein coupled. Numerous crystal structures have been reported for the neurotensin receptor 1 (NTS1). The third receptor has a single transmembrane domain and is encoded by the SORT1 gene.
The galanin receptor is a G protein-coupled receptor, or metabotropic receptor which binds galanin.
The oxytocin receptor, also known as OXTR, is a protein which functions as receptor for the hormone and neurotransmitter oxytocin. In humans, the oxytocin receptor is encoded by the OXTR gene which has been localized to human chromosome 3p25.
The μ-opioid receptors (MOR) are a class of opioid receptors with a high affinity for enkephalins and beta-endorphin, but a low affinity for dynorphins. They are also referred to as μ(mu)-opioid peptide (MOP) receptors. The prototypical μ-opioid receptor agonist is morphine, the primary psychoactive alkaloid in opium and for which the receptor was named, with mu being the first letter of Morpheus, the compound's namesake in the original Greek. It is an inhibitory G-protein coupled receptor that activates the Gi alpha subunit, inhibiting adenylate cyclase activity, lowering cAMP levels.
Carbetocin, sold under the brand names Pabal among others, is a medication used to prevent excessive bleeding after childbirth, particularly following Cesarean section. It appears to work as well as oxytocin. Due to it being less economical than other options, use is not recommended by NHS Scotland. It is given by injection into a vein or muscle.
G protein-coupled receptor 119 also known as GPR119 is a G protein-coupled receptor that in humans is encoded by the GPR119 gene.
A serenic, or anti-aggressive drug, is a type of drug which reduces the capacity for aggression.
WAY-267464 is a potent, selective, non-peptide agonist for the oxytocin receptor, with negligible affinity for the vasopressin receptors. Contradictorily however, though originally described as selective for the oxytocin receptor and lacking affinity for the vasopressin receptors, it has since been reported to also act as a potent vasopressin V1A receptor antagonist. WAY-267464 has been shown to cross the blood–brain barrier to a significantly greater extent than exogenously applied oxytocin, and in animal tests produces centrally-mediated oxytocinergic actions such as anxiolytic effects, but with no antidepressant effect evident. It was developed by a team at Ferring Pharmaceuticals. WAY-267464 was under investigation for the potential clinical treatment of anxiety disorders by Wyeth, and reached the preclinical stage of development, but no development has been reported as of 2011.
SKF-77,434 is a drug which acts as a selective dopamine D1 receptor partial agonist, and has stimulant and anorectic effects. Unlike other D1 agonists with higher efficacy such as SKF-81,297 and 6-Br-APB, SKF-77,434 does not maintain self-administration in animal studies, and so has been researched as a potential treatment for cocaine addiction.
Diarylpropionitrile (DPN), also known as 2,3-bis(p-hydroxyphenyl)propionitrile (2,3-BHPPN), is a synthetic, nonsteroidal, and highly selective agonist of ERβ (IC50 = 15 nM) that is used widely in scientific research to study the function of this receptor. It is 70-fold more selective for ERβ over ERα, and has 100-fold lower affinity for GPER (GPR30) relative to estradiol. DPN produces antidepressant- and anxiolytic-like effects in animals via activation of the endogenous oxytocin system. First reported in 2001, DPN was the first selective ERβ agonist to be discovered, and was followed by prinaberel (ERB-041, WAY-202041), WAY-200070, and 8β-VE2 in 2004, ERB-196 (WAY-202196) in 2005, and certain phytoestrogens like liquiritigenin and nyasol (cis-hinokiresinol) since 2007.
Synthetic oxytocin, sold under the brand name Pitocin among others, is a medication made from the peptide oxytocin. As a medication, it is used to cause contraction of the uterus to start labor, increase the speed of labor, and to stop bleeding following delivery. For this purpose, it is given by injection either into a muscle or into a vein.
LIT-001 is a small-molecule oxytocin receptor agonist and vasopressin receptor mixed agonist and antagonist that was first described in the literature in 2018. Along with TC OT 39 and WAY-267464, it is one of the first small-molecule oxytocin receptor agonists to have been developed. LIT-001 has greatly improved pharmacokinetic properties relative to oxytocin, reduces social deficits in animal models, and may have potential as a therapeutic agent in the treatment of social disorders like autism in humans.
