Dopamine receptor

The dopamine receptor is the receiving unit for signals by the neurotransmitter dopamine. The receptor is located on the cell surface, among others, particular neurons and smooth muscle cells of specific renal vessels. Now known five different forms of the dopamine receptor. Here D1 and D2 receptors are quantitatively the most common subtypes dar. These differ by the different signal path ( so-called second messenger ) from the receptor into the cell and by different pharmacological suggestibility. The influence of dopamine receptors by known agonists or antagonists, plays an important role in the treatment of Parkinson's disease, and vomiting upon treatment with neuroleptic drugs. Mutations in the DRD2 gene are associated with alcoholism and myoclonic dystonia.

Group classification

It differs due to the different intracellular signaling pathway and effect two groups of dopamine receptors:

Subtypes of the dopamine receptor

• D1 occurs on smooth muscle cells of renal and Mesenterialgefäßen, basal ganglia, the nucleus accumbens and cerebral cortex. It causes a dilation of the renal and mesenteric vessels and thus increased perfusion of the kidney and intestine
• D2 is found postrema in the nucleus accumbens, striatum, the anterior pituitary and the Area. In the anterior pituitary dopamine inhibits about the release of the hormone prolactin, in the area postrema vomiting is mediated via activation triggered. In addition, positive and negative symptoms of schizophrenia are mediated via the D2 receptor.
• D3 occurs in the cerebellum and inhibits adenylyl cyclases; it is the target of various drugs used to treat schizophrenia, dependence syndrome and Parkinson 's disease. D3 agonists, such as 7-OH -DPAT, rotigotine, pramipexole, and show, among other anti-depressant effects in rodent models of depression.
• D4 comes in the hippocampus, the frontal lobes and the amygdala before.
• D5 exists in the hippocampus and the amygdala.

Structure

Dopamine receptors are proteins that are characterized by their central structural motif, the seven cell membrane- spanning helices that. This postulated structure was confirmed for the D3 receptor with the help of the crystal structure analysis.

Pharmacology

The different pharmacology of the following substances is partly explained by the different distribution of substances into the brain across the blood- brain barrier. For example gets infused dopamine is not directly into the brain, apomorphine predominantly only in the region of the area postrema. The area postrema is a circumventricular organs of the so-called. Here there is a disruption of the blood -brain barrier.

• Dopamine: Dopamine excites especially in infusion D1 receptors in the kidney and Mesenterialgefäßen and thus initially increases the blood circulation in the kidneys and in the intestine. At higher dosage then also effects on adrenoceptors.
• Apomorphine: Apomorphine activates D2 receptors. Use mainly to compensate for the dopamine deficit in Parkinson's disease. Strong trigger of nausea.
• Bromocriptine: Bromocriptine activates the D2 receptor. Use, among others, in Parkinson's disease, weaning ( inhibits prolactin education). Side effects include nausea and vomiting.
• Metoclopramide and domperidone: metoclopramide blocked including the D2 receptor in the area postrema and thereby inhibits the induction of vomiting. Domperidone accelerates well under inhibition of the D2 receptor, the stomach movement toward the duodenum. Application of both substances are therefore as so-called anti-emetics in relapsed and vomiting as prokinetic agents.
• Haloperidol, acepromazine and other neuroleptics: These inhibit mainly the D2 receptor (possibly D4 and D3). Used, inter alia in schizophrenia and arousal states.
• Clozapine: Clozapine is an atypical antipsychotic drug and inhibits primarily the D4 receptor. It occurs, for example in schizophrenia used.
• Pramipexole enabled to D3 receptors in the limbic system and the frontal cortex.