title: Mechanism of action of histamine in the estrogen-primed rat uterus.
abstract: Histamine produced a dose-dependent relaxation of uterine strips obtained from the estrogen-primed rat uterus. The responses to histamine were blocked competitively by metiamide (10(-8)-10(-8) M), a specific H2-receptor antagonist. Propranolol, a selective beta-receptor blocker also produced competitive antagonism of the responses to histamine in the same dose range (10(-8)-10(-6) M). The pA2 value obtained for metiamide (8.9) was not significantly different from that obtained for propranolol (8.6). Nialamide (2.2 X 10(-6) M), the monoamine oxidase inhibitor, and cocaine (4.3 X 10(-6) M), the selective noradrenaline uptake blocker, potentiated the responses to histamine. However bretylium (2.4 X 10(-5) M), and adrenergic neuron blocker inhibited the responses to histamine. The combined effect of tyramine and histamine was found to be additive. Our data suggest that the histamine-induced relaxation of rat uterus may be produced through the stimulation of presynaptic H2-receptors which causes the release of noradrenaline. The released noradrenaline acts on the postsynaptic beta-receptors and produces relaxation of the rat uterus.
mesh_terms: D000818:Animals; D004054:Diethylstilbestrol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006632:Histamine / Q000494:pharmacology*; D006633:Histamine Antagonists; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D014599:Uterus / Q000187:drug effects*
chemical_list: D006633:Histamine Antagonists; D004054:Diethylstilbestrol; D006632:Histamine