Do H3-receptors participate in the effects of histamine on electrically-evoked contractions of rat vas deferens?
1. The specific effects of histamine were studied on rat vas deferens contractions induced by electrical field stimulation (0.1 Hz, 1 pulse, 1 msec duration, supramaximal voltage). 2. Histamine (5 x 10(-7)-10(-4) M) inhibited the electrically-evoked contractions (EEC). This effect was unchanged after the H1-receptor antagonist diphenhydramine (5 x 10(-6) M) and was decreased after the H2-receptor antagonist cimetidine (10(-5) M). 3. Betahistine, described as H1-agonist (in guinea pig ileum) and H3-autoreceptor antagonist (in rat cerebral cortex) slightly decreased the EEC, but competitively inhibited the histamine effect. 4. The results obtained suggest the existence of a specific third type presynaptic H-receptors in rat vas deferens, which are pharmacologically similar to the presynaptic H3-autoreceptors in rat cerebral cortex.
Vassilev
P
P
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Staneva-Stoytcheva
D
D
Mutafova-Yambolieva
V
V
D000818:Animals; D001621:Betahistine / Q000494:pharmacology; D004155:Diphenhydramine / Q000494:pharmacology; D004558:Electric Stimulation; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011968:Receptors, Histamine / Q000187:drug effects / Q000502:physiology*; D018100:Receptors, Histamine H3; D014649:Vas Deferens / Q000187:drug effects* / Q000502:physiology
D011968:Receptors, Histamine; D018100:Receptors, Histamine H3; D006632:Histamine; D004155:Diphenhydramine; D001621:Betahistine