A dopamine antagonist, also known as an anti-dopaminergic and a dopamine receptor antagonist (DRA), is a type of drug which blocks dopamine receptors by receptor antagonism. Most antipsychotics are dopamine antagonists, and as such they have found use in treating schizophrenia, bipolar disorder, and stimulant psychosis. Several other dopamine antagonists are antiemetics used in the treatment of nausea and vomiting.
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-HT3 receptor belongs to the Cys-loop superfamily of ligand-gated ion channels (LGICs) and therefore differs structurally and functionally from all other 5-HT receptors (5-hydroxytryptamine, or serotonin receptors) which are G protein-coupled receptors. This ion channel is cation-selective and mediates neuronal depolarization and excitation within the central and peripheral nervous systems.
The 5-HT3 antagonists, informally known as "setrons", are a class of drugs that act as receptor antagonists at the 5-HT3 receptor, a subtype of serotonin receptor found in terminals of the vagus nerve and in certain areas of the brain. With the notable exceptions of alosetron and cilansetron, which are used in the treatment of irritable bowel syndrome, all 5-HT3 antagonists are antiemetics, used in the prevention and treatment of nausea and vomiting. They are particularly effective in controlling the nausea and vomiting produced by cancer chemotherapy and are considered the gold standard for this purpose.
Metopimazine, sold under the brand names Vogalen and Vogalene, is an antiemetic of the phenothiazine group which is used to treat nausea and vomiting. It is marketed in Europe, Canada, and South America. As of August 2020, metopimazine has been repurposed and is additionally under development for use in the United States for the treatment of gastroparesis.
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.
Dopamine receptor D3 is a protein that in humans is encoded by the DRD3 gene.
Zacopride is a potent antagonist at the 5-HT3 receptor and an agonist at the 5-HT4 receptor. It has anxiolytic and nootropic effects in animal models, with the (R)-(+)-enantiomer being the more active form. It also has antiemetic and pro-respiratory effects, both reducing sleep apnea and reversing opioid-induced respiratory depression in animal studies. Early animal trials have also revealed that administration of zacopride can reduce preference for and consumption of ethanol.
Blonanserin, sold under the brand name Lonasen, is a relatively new atypical antipsychotic commercialized by Dainippon Sumitomo Pharma in Japan and Korea for the treatment of schizophrenia. Relative to many other antipsychotics, blonanserin has an improved tolerability profile, lacking side effects such as extrapyramidal symptoms, excessive sedation, or hypotension. As with many second-generation (atypical) antipsychotics it is significantly more efficacious in the treatment of the negative symptoms of schizophrenia compared to first-generation (typical) antipsychotics such as haloperidol.
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.
Litoxetine (developmental code names SL 81-0385, IXA-001) is an antidepressant which was under clinical development for the treatment of depression in the early 1990s but was never marketed. It acts as a potent serotonin reuptake inhibitor (Ki for SERTTooltip serotonin transporter = 7 nM) and modest 5-HT3 receptor antagonist (Ki = 315 nM). It has antiemetic activity, and unlike the selective serotonin reuptake inhibitors (SSRIs), appears to have a negligible incidence of nausea and vomiting. The drug is structurally related to indalpine. Development of litoxetine for depression was apparently ceased in the late 1990s. However, as of March 2017, development of litoxetine has been reinitiated and the drug is now in the phase II stage for the treatment of urinary incontinence.
Ricasetron (BRL-46470) is a drug which acts as a selective antagonist at the serotonin 5-HT3 receptor. It has antiemetic effects as with other 5-HT3 antagonists, and also has anxiolytic effects significantly stronger than other related drugs, and with less side effects than benzodiazepine anxiolytics. However, it has never been developed for medical use.
7-OH-DPAT is a synthetic compound that acts as a dopamine receptor agonist with reasonable selectivity for the D3 receptor subtype, and low affinity for serotonin receptors, unlike its structural isomer 8-OH-DPAT. 7-OH-DPAT is self-administered in several animal models, and is used to study its addiction effects to cocaine.
Batanopride (BMY-25,801) is an antiemetic drug of the benzamide class which acts as a selective 5-HT3 receptor antagonist. It was trialled to reduce nausea during cancer chemotherapy, but was never approved for medical use due to dose-limiting side effects including hypotension and long QT syndrome.
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.
L-741,626 is a drug which acts as a potent and selective antagonist for the dopamine receptor D2. It has good selectivity over the related D3 and D4 subtypes and other receptors. L-741,626 is used for laboratory research into brain function and has proved particularly useful for distinguishing D2 mediated responses from those produced by the closely related D3 subtype, and for studying the roles of these subtypes in the action of cocaine and amphetamines in the brain.
Clorotepine, also known as octoclothepin or octoclothepine, is an antipsychotic of the tricyclic group which was derived from perathiepin in 1965 and marketed in the Czech Republic by Spofa in or around 1971 for the treatment of schizophrenic psychosis.
MGS-0039 is a drug that is used in neuroscientific research, which acts as a potent and selective antagonist for group II of the metabotropic glutamate receptors (mGluR2/3). It produces antidepressant and anxiolytic effects in animal studies, and has been shown to boost release of dopamine and serotonin in specific brain areas. Research has suggested this may occur through a similar mechanism as that suggested for the similarly glutamatergic drug ketamine.
Amesergide is a serotonin receptor antagonist of the ergoline and lysergamide families related to methysergide which was under development by Eli Lilly and Company for the treatment of a variety of conditions including depression, anxiety, schizophrenia, male sexual dysfunction, migraine, and thrombosis but was never marketed. It reached phase II clinical trials for the treatment of depression, erectile dysfunction, and premature ejaculation prior to the discontinuation of its development.
