1989 Volume 49 Issue 4 Pages 531-534
In the HEPES-buffered physiological solution containing 20 mM bicarbonate ion, cocaine not only increased the sensitivity to norepinephrine but enhanced the maximal contractions to norepinephrine and methacholine in the rat vas deferens. Cocaine also potentiated the high potassium-induced contractions. In the solution without bicarbonate ion, such effects of cocaine were lost except for the sensitivity increase to norepinephrine. These results suggest that bicarbonate ion is crucial for the postjunctional stimulatory action of cocaine in the rat vas deferens.