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Dopamine receptor types
There are five types of dopamine receptor.
The D1 and D5 receptors are members of the D1-like family of dopamine receptors whereas the D2, D3 and D4 receptors are members of the D2-like family.
- D1-like: Activation of the D1-like family receptors is coupled to increases in cAMP and is typically excitatory.
- D2-like: D2-like activation reduces cAMP and is typically inhibitory.
- D2 ("DRD2", OMIM 126450). There is a short version of D2 (D2Sh) and a long version of D2 (D2Lh). The D2Sh are pre-synaptic situated, having modulatory functions (called autoreceptor, they regulates the neurotransmission by feed-back mechanisms, i.e., synthesis, storage and release of dopamine into the synaptic cleft) and the D2Lh, which may have the classic function of a post-synaptic receptor, i.e., keep going on the neurotransmission (excitatory or inhibitory) once blocked by a receptor antagonist or stimulated by the endogenous neurotransmitter itself or a synthetic full or partial agonist.
- D3 ("DRD3", OMIM 126451)
- D4 ("DRD4", OMIM 126452). D4 has the following variants D4.2, D4.3a, D4.3b, D4.4a, D4.4b, D4.4c, D4.4d, D4.4e, D4.5a, D4.5b, D4.6a, D4.6b, D4.7a, D4.7b, D4.7c, D4.7d, D4.8, D4.10.
All are G protein coupled metabotropic receptors, and can be excitatory or inhibitory to the post-synaptic neuron.
In schizophrenics and patients with Tardive dysphrenia, D2 receptors are supposed to exist in higher than normal levels on the dopaminergic mesolimbic pathway, and antipsychotic drugs which aim to block these may cause its upregulation.
In patients with Tourettes Syndrome, studies show that the severity of the patient's tics may be directly correlated with the amount of binding of D2 Dopamine receptors in the Caudate nucleus.
- Zimmerberg, B., "Dopamine receptors: A representative family of metabotropic receptors, Multimedia Neuroscience Education Project (2002)
- FROTA LH. "Partial Agonists in the Schizophrenia Armamentarium. Tardive Dysphrenia: The newest challenge to the last generation atypical antipsychotics drugs?" J Bras Psiquiatr 2003; Vol 52 Supl 1;14-24.
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