Aripiprazole, sold under the brand names Abilify and Aristada, among others, is an atypical antipsychotic. It is primarily used in the treatment of schizophrenia and bipolar disorder; other uses include as an add-on treatment in major depressive disorder and obsessive compulsive disorder (OCD), tic disorders, and irritability associated with autism. Aripiprazole is taken by mouth or via injection into a muscle. A Cochrane review found low-quality evidence of effectiveness in treating schizophrenia.
The dopamine hypothesis of schizophrenia or the dopamine hypothesis of psychosis is a model that attributes the positive symptoms of schizophrenia to a disturbed and hyperactive dopaminergic signal transduction. The model draws evidence from the observation that a large number of antipsychotics have dopamine-receptor antagonistic effects. The theory, however, does not posit dopamine overabundance as a complete explanation for schizophrenia. Rather, the overactivation of D2 receptors, specifically, is one effect of the global chemical synaptic dysregulation observed in this disorder.
Dopamine receptors are a class of G protein-coupled receptors that are prominent in the vertebrate central nervous system (CNS). Dopamine receptors activate different effectors through not only G-protein coupling, but also signaling through different protein interactions. The neurotransmitter dopamine is the primary endogenous ligand for dopamine receptors.
SKF-82,958 is a synthetic compound of the benzazepine class that acts as a D1/D5 receptor full agonist. SKF-82,958 and similar D1-like-selective full agonists like SKF-81,297 and 6-Br-APB produce characteristic anorectic effects, hyperactivity and self-administration in animals, with a similar but not identical profile to that of dopaminergic stimulants such as amphetamine. SKF-82,958 was also subsequently found to act as an agonist of ERα with negligible activity at ERβ, making it a subtype-selective estrogen.
A dopamine agonist(DA) is a compound that activates dopamine receptors. There are two families of dopamine receptors, D1-like and D2-like. They are all G protein-coupled receptors. D1- and D5-receptors belong to the D1-like family and the D2-like family includes D2, D3 and D4 receptors. Dopamine agonists are primarily used in the treatment of Parkinson's disease, and to a lesser extent, in hyperprolactinemia and restless legs syndrome. They are also used off-label in the treatment of clinical depression. The use of dopamine agonists is associated with impulse control disorders and dopamine agonist withdrawal syndrome (DAWS).
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.
Dihydroergocryptine (DHEC), sold under the brand names Almirid and Cripar among others, is a dopamine agonist of the ergoline group that is used as an antiparkinson agent in the treatment of Parkinson's disease. It is taken by mouth.
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.
Dopamine receptor D1, also known as DRD1. It is one of the two types of D1-like receptor family — receptors D1 and D5. It is a protein that in humans is encoded by the DRD1 gene.
The glutamate hypothesis of schizophrenia models the subset of pathologic mechanisms of schizophrenia linked to glutamatergic signaling. The hypothesis was initially based on a set of clinical, neuropathological, and, later, genetic findings pointing at a hypofunction of glutamatergic signaling via NMDA receptors. While thought to be more proximal to the root causes of schizophrenia, it does not negate the dopamine hypothesis, and the two may be ultimately brought together by circuit-based models. The development of the hypothesis allowed for the integration of the GABAergic and oscillatory abnormalities into the converging disease model and made it possible to discover the causes of some disruptions.
UH-232 ((+)-UH232) is a drug which acts as a subtype selective mixed agonist-antagonist for dopamine receptors, acting as a weak partial agonist at the D3 subtype, and an antagonist at D2Sh autoreceptors on dopaminergic nerve terminals. It causes dopamine release in the brain and has a stimulant effect, as well as blocking the behavioural effects of cocaine. It may also serve as a 5-HT2A receptor agonist, based on animal studies. It was investigated in clinical trials for the treatment of schizophrenia, but unexpectedly caused symptoms to become worse.
6-Br-APB is a synthetic compound that acts as a selective D1 agonist, with the (R)-enantiomer being a potent full agonist, while the (S) enantiomer retains its D1 selectivity but is a weak partial agonist. (R)-6-Br-APB and similar D1-selective full agonists like SKF-81,297 and SKF-82,958 produce characteristic anorectic effects, stereotyped behaviour and self-administration in animals, with a similar but not identical profile to that of dopaminergic stimulants such as amphetamine.
A-77636 is a synthetic drug which acts as a selective D1 receptor full agonist. It has nootropic, anorectic, rewarding and antiparkinsonian effects in animal studies, but its high potency and long duration of action causes D1 receptor downregulation and tachyphylaxis, and unlike other D1 full agonists such as SKF-82,958, it does not produce place preference in animals. A-77636 partially substituted for cocaine in animal studies, and has been suggested for use as a possible substitute drug in treating addiction, but it is better known for its use in studying the role of D1 receptors in the brain.
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.
Sarizotan (EMD-128,130) is a selective 5-HT1A receptor agonist and D2 receptor antagonist, which has antipsychotic effects, and has also shown efficacy in reducing dyskinesias resulting from long-term anti-Parkinsonian treatment with levodopa.
PNU-99,194(A) (or U-99,194(A)) is a drug which acts as a moderately selective D3 receptor antagonist with ~15-30-fold preference for D3 over the D2 subtype. Though it has substantially greater preference for D3 over D2, the latter receptor does still play some role in its effects, as evidenced by the fact that PNU-99,194 weakly stimulates both prolactin secretion and striatal dopamine synthesis, actions it does not share with the more selective (100-fold) D3 receptor antagonists S-14,297 and GR-103,691.
Cariprazine, sold under the brand names Vraylar, Reagila and Symvenu among others, is an atypical antipsychotic developed by Gedeon Richter, which is used in the treatment of schizophrenia, bipolar mania, bipolar depression, and major depressive disorder. It acts primarily as a D3 and D2 receptor partial agonist, with a preference for the D3 receptor. Cariprazine is also a partial agonist at the serotonin 5-HT1A receptor and acts as an antagonist at 5-HT2B and 5-HT2A receptors, with high selectivity for the D3 receptor. It is taken by mouth.
5-OH-DPAT is a synthetic compound that acts as a dopamine receptor agonist with selectivity for the D2 receptor and D3 receptor subtypes. Only the (S)-enantiomer is active as an agonist, with the (R)-enantiomer being a weak antagonist at D2 receptors. Radiolabelled 11C-5-OH-DPAT is used as an agonist radioligand for mapping the distribution and function of D2 and D3 receptors in the brain, and the drug is also being studied in the treatment of Parkinson's disease.
A prolactin modulator is a drug which affects the hypothalamic–pituitary–prolactin axis by modulating the secretion of the pituitary hormone prolactin from the anterior pituitary gland. Prolactin inhibitors suppress and prolactin releasers induce the secretion of prolactin, respectively.
3-PPP (N-n-propyl-3-(3-hydroxyphenyl)piperidine) is a mixed sigma σ1 and σ2 receptor agonist (with similar affinity for both subtypes, though slightly higher affinity for the latter) and D2 receptor partial agonist which is used in scientific research. It shows stereoselectivity in its pharmacodynamics. (+)-3-PPP is the enantiomer that acts as an agonist of the sigma receptors; it is also an agonist of both D2 presynaptic and postsynaptic receptors. Conversely, (−)-3-PPP, also known as preclamol (INNTooltip International Nonproprietary Name), acts as an agonist of presynaptic D2 receptors but as an antagonist of postsynaptic D2 receptors, and has antipsychotic effects. 3-PPP has also been reported to be a monoamine reuptake inhibitor and possibly to act at adrenergic receptors or some other non-sigma receptor.
