The effects of nicorandil on phasic contractions of isolated canine coronary artery.

The effects of nicorandil on the phasic contractions of canine coronary smooth muscles were compared with the effects of other vasodilating agents. Phasic contractions of the smooth muscles were induced by applying 10(-2) M 3,4-diaminopyridine, a potassium channel blocker. The peak tension of phasic contractions was reduced by 10(-6) M and phasic contractions were eliminated by 10(-4) M of nicorandil. The peak tension was also reduced by 10(-8) M nitroglycerin, 10(-7) M nifedipine, and 10(-5) M W-7. Phasic contractions were eliminated by 10(-6) M nifedipine and 10(-4) M W-7, but they were not eliminated by 10(-6) M nitroglycerin. Depolarization associated with the phasic contractions was eliminated by 10(-6) M nifedipine and 10(-4) M nicorandil. These results indicate that nicorandil eliminated the phasic contractions of canine coronary smooth muscles through inhibition of depolarization, just as does nifedipine. It is likely that nicorandil inhibited depolarization through an increase in potassium conductance.