Study of the possible effects of diltiazem a calcium channel blocker versus pinacidil a potassium channel activator on the response of some vascular and non-vascular isolated smooth muscle preparations to their neurotransmitters

ABSTRACT

The effects of the Ca 2+ channel blocker diltiazem were investigated and compared with those of pinacidil a K + channel activator on the agonist-induced contractions of the isolated rabbit aortic strip, rat fundus, guinea pig ileum and tracheal chain. Both diltiazem and pinacidil showed a concentration-dependent inhibition of the norepinephrine [NE]-induced contraction of the isolated rabbit aortic strip. The effective concentration [EC50] of diltiazem was 6 x 10 -6 mmol +/- 0.39 and that of pinacidil was 4 x 10 -5 mmol +/- 0.02. Diltiazem and pinacidil, even at high concentrations, were without any effect on the agonist induced contractions of the different non-vascular smooth muscle preparations used in the study. The results suggested that the antispamogenic effect of diltiazem and pinacidil may be restricted to the vascular smooth muscle fibers, since both drugs failed to inhibit the response of non-vascular smooth muscle preparation to their agonists