title: A postsynaptic inhibitory histamine H2-receptor in the mouse isolated vas deferens.
abstract: The effect of histamine on adrenergic neurotransmission in the mouse isolated vas deferens preparation was investigated. Concentrations of histamine ranging from 0.2 to 650 microM depressed, in a dose-related manner, not only the contractile response elicited by field stimulation but also the response caused by the addition of exogenous noradrenaline and acetylcholine. However, the release of [3H]-NA evoked by field stimulation or by high K+ remained unchanged in the presence of these concentrations of histamine. The inhibitory effect of histamine on the contractile responses caused by various stimuli was reduced or completely antagonized by cimetidine, a histamine H2-receptor antagonist but not by mepyramine, a conventional antihistamine. The inhibitory effect of histamine was found to be inversely proportional to both the Ca2+ concentration in the bathing medium and to the frequency of field stimulation. Further, the inhibitory effect of histamine was markedly reduced when Mg2+ was omitted from the bathing medium. It is concluded that the mouse vas deferens preparation contains a post-junctional inhibitory H2-receptor. The stimulation of H2-receptors by histamine inhibits the contractile response of the vas deferens, possibly by decreasing the availability of Ca2+ required for contraction by depressing the influx of Ca2+.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006632:Histamine / Q000494:pharmacology; D008274:Magnesium / Q000378:metabolism; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D011968:Receptors, Histamine; D011970:Receptors, Histamine H2; D017981:Receptors, Neurotransmitter; D013997:Time Factors; D014649:Vas Deferens / Q000378:metabolism*
chemical_list: D011968:Receptors, Histamine; D011970:Receptors, Histamine H2; D017981:Receptors, Neurotransmitter; D006632:Histamine; D008274:Magnesium; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine