The actions of cirazoline on the rat vas deferens

Abstract

1 The pre- and postsynaptic effects of the α₁-agonist cirazoline were assessed in epididymal and prostatic portions of the rat isolated vas deferens. 2 Cirazoline produced a postsynaptic α₁-adrenoceptor mediated potentiation of the isometric contraction to single pulse field stimulation in both prostatic and epididymal portions. 3 In epididymal portions, nifedipine (10 μM) greatly attenuated the postsynaptic α₁-receptor mediated potentiation of nerve mediated contractions, uncovering a presynaptic inhibitory action of cirazoline. 4 No evidence was found for α₂-antagonism by cirazoline. It is concluded that the previously reported antagonism of the presynaptic inhibitory effects of clonidine was due to postsynaptic potentiation of nerve-mediated responses by cirazoline.