title: Inhibition via muscarinic M-1 receptor stimulation of TRH-induced prolactin release in estrogen-primed rats.
abstract: The cholinergic mechanism involved in the regulation of prolactin secretion induced by thyrotropin-releasing hormone (TRH) in estrogen-primed male rats was investigated. Intraperitoneal injections of pharmacological doses of TRH (20 mg/kg), MK-771 (2 mg/kg) and DN-1417 (10 mg/kg) increased serum prolactin levels in estrogen-primed male rats, but not in nonprimed male rats. This increase was reduced by pilocarpine, a muscarinic M-1 receptor agonist, but not by carbachol, a M-2 receptor agonist. Pirenzepine, a peripheral M-1 receptor antagonist, did not affect TRH-induced prolactin release, but antagonized the inhibitory effect of pilocarpine. The results indicate that TRH and TRH analogues increase prolactin secretion in the estrogen-primed male rats and that a stimulation of muscarinic M-1 receptors exerts an inhibitory effect on the prolactin release induced by TRH in the estrogen primed male rats.
mesh_terms: D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology; D014150:Antipsychotic Agents / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D008297:Male; D010862:Pilocarpine / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000187:drug effects*; D053778:Thiazolidines; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000494:pharmacology*
chemical_list: D000928:Antidepressive Agents; D014150:Antipsychotic Agents; D004967:Estrogens; D011976:Receptors, Muscarinic; D053778:Thiazolidines; D010862:Pilocarpine; D013973:Thyrotropin-Releasing Hormone; C021597:pyro(l-alpha-aminoadipyl)-L-histidyl-L-thiazolidine-4-carboxamide; D011388:Prolactin; C029762:DN 1417