title: Identification and specific blockade of histaminergic receptors in guinea pig vasa deferentia.
abstract: Histamine produces contractions of the guinea pig vas deferens. The present investigation was undertaken to characterize the nature of histaminergic receptors in this tissue. Histamine (1.6 X 10(-6) M to 3.2 X 10(-5) M) produced dose-related contractions of guinea pig vas deferens (GPVD). Mepyramine (5.3 X 10(-8) M and 1 X 10(-9) M) blocked the responses to histamine competitively. Metiamide (1.23 X 10(-5) M) did not block the responses to histamine significantly. Specific H1 and H2 receptor agonists, namely 2-(2'-pyridyl)ethylamine (PEA) (2.55 X 10(-6) M to 3.0 X 10(-5) M) and 4-methylhistamine (4-MH) (2.52 X 10(-5) M to 3.0 X 10(-4) M), respectively, produced dose-related contractions of GPVD. The responses to PEA were blocked competitively by mepyramine, whereas the responses to 4-MH were blocked by metiamide. Reserpine pretreatment (5 mg/kg, i.p., 24 h) did not alter the responses to histamine and PEA. Our data suggest the presence of both H1 and H2 receptors in the GPVD which are excitatory in nature.
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D006635:Histamine H2 Antagonists / Q000494:pharmacology*; D008297:Male; D008761:Methylhistamines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D011968:Receptors, Histamine / Q000378:metabolism*; D011969:Receptors, Histamine H1 / Q000187:drug effects; D012110:Reserpine / Q000494:pharmacology; D014649:Vas Deferens / Q000378:metabolism*
chemical_list: D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D008761:Methylhistamines; D011725:Pyridines; D011968:Receptors, Histamine; D011969:Receptors, Histamine H1; C025566:4-methylhistamine; D012110:Reserpine; C006183:2-(2-aminoethyl)pyridine; D011738:Pyrilamine