Effects of cocaine on Ca-mobility in microsomal fraction from rat vas deferens

Cocaine (3 x 10(-5) M) has been reported to potentiate maximal contraction induced by several stimulants, and this phenomenon might be ascribed to the postsynaptic action. The present study was undertaken to observe the influences of cocaine on Ca-movements, that is, Ca-uptake and Ca-release, in the microsomal fraction of the prostatic half of the rat vas deferens. In this study, it was shown that cocaine potentiated Ca-uptake at the lower concentration (10(-6) M) of Ca2+, but had no influence upon Ca-release and also that cocaine significantly increased the rate of Ca-uptake. These results suggest that cocaine promotes binding of Ca ions with the surface sites of smooth muscle membrane concerned with Ca-influx process and thereby potentiates maximal contractions elicited by different stimulants.