[Effects of vasodilators on cyclic contraction induced by 3,4-diaminopyridine in isolated porcine coronary arteries].
3,4-Diaminopyridine (3,4-DAP), which is known to decrease K conductance, produced spontaneous repetitive phasic contractions of a regular (28/60) and an irregular (15/60) cycle or tonic contraction (16/60) following a latent period of 5-100 min in isolated porcine coronary arteries. Effects of pinacidil, a newly-synthesized vasodilator, were investigated using the preparation in which 3,4-DAP produced phasic contractions of the regular cycle in comparison with those of various vasodilators. Pinacidil produced dose-dependent prolongation of the cycle and reduced the peak tension and the tension at the relaxation phase, a mode of action that closely resembles that of nicorandil, suggesting the increase in K conductance and hyperpolarization. Nifedipine (10(-8) M) and dilazep (10(-4) M) markedly reduced the peak tension, while adenosine, dipyridamole and nitroglycerin did not produce such effects. The latter three drugs produced a prolongation of the cycle and reduced the tension of the relaxation phase. These data suggest that reduction of K conductance and activation of the voltage-dependent Ca channel may play an important role in initiation of the spontaneous repetitive phasic contraction in porcine coronary artery.
D015761:4-Aminopyridine / Q000031:analogs & derivatives*; D000077770:Amifampridine; D000631:Aminopyridines / Q000494:pharmacology*; D000787:Angina Pectoris / Q000503:physiopathology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003331:Coronary Vessels / Q000187:drug effects* / Q000502:physiology; D004347:Drug Interactions; D006146:Guanidines / Q000494:pharmacology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology; D010507:Periodicity; D020110:Pinacidil; D011188:Potassium / Q000378:metabolism; D013552:Swine; D014665:Vasodilator Agents / Q000494:pharmacology*
D000631:Aminopyridines; D006146:Guanidines; D007473:Ion Channels; D014665:Vasodilator Agents; D020110:Pinacidil; D015761:4-Aminopyridine; D000077770:Amifampridine; D011188:Potassium; D002118:Calcium