In vitro effects of catachol amines on the vas deferens of guinea pigs

ABSTRACT

Adrenaline and Noradrenaline both caused a contraction of the vas deferens. However, adrenaline was a more potent stimulant than noradrenaline. Isoprenaline by itself had no effect on the vas deferens, but it modified the stimulatory effect of subsequent administered adrenaline and noradrenaline. In small doses isoprenaline lessened and in large doses it potentiated the stimulating effect of the other two amines, the degree of inhibition by isoprenaline being greater on noradrenaline than on adrenaline. It was suggested that isoprenaline acted by inhibiting alpha adrenergic receptors in small concentrations, stimulating them in large concentrations and not by stimulating Beta receptors as is presently believed (AU)