Inhibition of the TSH secretion by histamine in male rats.
The effect of histamine (HA) on the cold-stimulated and the TRH-induced TSH secretion was studied in male rats utilizing HA and specific HA antagonists and histaminergic drugs as tools. L-histidine (1000 and 1500 mg/kg ip) inhibited the cold-stimulated but not the TRH-induced TSH secretion. Mepyramine (5-50 mg/kg ip) and cimetidine (50-250 mg/kg ip) had no effect on the TSH-cold-response, but the TRH-induced TSH secretion was enhanced by them. HA (1 mg/kg sc), 2-pyridylethylamine (2PEA; 10 mg/kg ip) and impromidine (1 mg/kg sc) decreased the TRH-induced TSH secretion but did not affect the TSH cold-response. When infused into the third ventricle HA (1-50 micrograms/rat), impromidine (0.1 and 1.0 microgram/rat) and 2PEA (50 micrograms/rat) decreased the cold-stimulated TSH-secretion. The locus of the inhibitory action of HA seems to be both at the anterior pituitary, where it is mediated through H1- and H2-receptors and in the hypothalamus, where the effect appears to be mediated through H2-receptors. At least a part of this particular action might be explained by other mechanisms since neither H1- nor H2-receptor antagonists were able to counteract the effect of HA.
D000818:Animals; D002927:Cimetidine / Q000494:pharmacology; D003080:Cold Temperature; D006632:Histamine / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology*; D006639:Histidine / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D017446:Impromidine; D008297:Male; D011725:Pyridines / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011968:Receptors, Histamine / Q000187:drug effects*; D011969:Receptors, Histamine H1 / Q000187:drug effects*; D011970:Receptors, Histamine H2 / Q000187:drug effects*; D013972:Thyrotropin / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D006633:Histamine Antagonists; D007093:Imidazoles; D011725:Pyridines; D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D006639:Histidine; D013973:Thyrotropin-Releasing Hormone; D002927:Cimetidine; D006632:Histamine; D013972:Thyrotropin; D017446:Impromidine; C006183:2-(2-aminoethyl)pyridine; D011738:Pyrilamine