Involvement of calcium ions in the modulation of electrically-induced rat vas deferens contractions by histaminergic drugs.
1. The modulatory action of histaminergic drugs: histamine; 2-(2-aminoethyl)thiazole (H1-agonist); dimaprit (H2-agonist); diphenhydramine (H1-receptor antagonist); and cimetidine (H2-receptor antagonist) on rat vas deferens contractions induced by electrical field stimulation (0.1 Hz, 1 pulse, 1 msec duration, supramaximal voltage) was studied either at different calcium concentrations in the nutrient fluid or after verapamil. 2. Histamine and 2-(2-aminoethyl)thiazole inhibited the electrically-evoked contractions (EEC). This effect was unchanged after verapamil. 3. Diphenhydramine potentiated the EEC. Verapamil added before the H1-receptor antagonist inhibited this action. 4. The effects of agonists and antagonists of H-receptors decreased with the increasing of calcium concentration. 5. The results obtained suggested the existence of heterogeneity of prejunctional H-receptors. The function of histaminergic drugs on adrenergic neurotransmission in field stimulated rat vas deferens is Ca(2+)-dependent.
Vassilev
P
P
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Mutafova-Yambolieva
V
V
Staneva-Stoytcheva
D
D
Todorov
S
S
D000818:Animals; D002118:Calcium / Q000008:administration & dosage / Q000378:metabolism*; D002927:Cimetidine / Q000494:pharmacology; D017259:Dimaprit; D004155:Diphenhydramine / Q000494:pharmacology; D004558:Electric Stimulation; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D051381:Rats; D011969:Receptors, Histamine H1 / Q000187:drug effects; D011970:Receptors, Histamine H2 / Q000187:drug effects; D013844:Thiazoles / Q000494:pharmacology; D013890:Thiourea / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects* / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D013844:Thiazoles; C029345:2-(2-aminoethyl)thiazole; D002927:Cimetidine; D006632:Histamine; D004155:Diphenhydramine; D014700:Verapamil; D013890:Thiourea; D002118:Calcium; D017259:Dimaprit