Modulation of dopamine receptors by thyrotropin-releasing hormone in the rat brain.
Nanomolar concentration of thyrotropin-releasing hormone (TRH) in vitro caused a significant reduction of [3H]apomorphine binding sites (70% of the control) in the rat striatum and the limbic forebrain. [3H]Spiperone binding was not affected by TRH. On the other hand, dopamine and apomorphine displaced [3H]TRH binding partially, suggesting the presence of a TRH receptor subpopulation that has a high affinity for dopamine agonist. Most of the neuroleptics displaced [3H]TRH binding dose-dependently in the micromolar range. (-)-Sulpiride had no affinity to TRH receptors. These findings suggest that one of the important roles of TRH as a neuromodulator is to modulate receptors for classical neurotransmitters, and this receptor-receptor interaction may be of importance in explaining the well known stimulating effects of TRH on the dopaminergic system.
D000818:Animals; D001058:Apomorphine / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009928:Organ Specificity; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects / Q000378:metabolism*; D017981:Receptors, Neurotransmitter / Q000378:metabolism; D018025:Receptors, Thyrotropin-Releasing Hormone; D013134:Spiperone / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism / Q000494:pharmacology*
D011954:Receptors, Dopamine; D017981:Receptors, Neurotransmitter; D018025:Receptors, Thyrotropin-Releasing Hormone; D013134:Spiperone; D013973:Thyrotropin-Releasing Hormone; D001058:Apomorphine