Effect of calcium antagonists on the response of the rat vas deferens to noradrenaline and field stimulation

Abstract

The effects of two calcium antagonists, Verapamil (VRP) and Methoxyverapamil (D-0600) on the contractile responses of the isolated rat vas deferens to norepinephrine (NE) and to field stimulation (FS) were studied.VRP (1 X 10(-06)-2 X 10(-06) M) decreased the responses to NE.It also decreased the amplitude of the FS elicited responses but only when 100 time higher doses were used.Similarly, D-0600 only reduced FS responses with equally high doses.In addition, when trains of pulses were used for FS, VRP (1 X 10(-5)-1 X 1(-4) M) caused an initial increase in the responses followed by a decrease.The fact that much higher doses of VRP are necessary to reduce the FS elicited responses than the contraction due to NE, suggests that the neurotransmitter released by FS might not be NE but a different one which seems to be much less dependent on external calcium than NE for producing its action.