The actions of cirazoline on the rat vas deferens

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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.