An analysis of the characteristics of the adrenergic neurone blocking action of dimethylphenylpiperazinium

An analysis of the characteristics of the adrenergic neurone blocking action of 1,1-dimethyl-4-phenylpiperazinium (DMPP) was undertaken using rat isolated vasa deferentia. DMPP (1x10^-6 to 1.5x10^-5 g/ml) reduced progressively the contractile response to transmural stimulation (TMS) in a dose-dependent manner without inhibiting the response to exogenous norepinephrine. The DMPP-induced inhibition was not reversed by washing but could be antagonized by dexamphetamine in a concentration which did not by itself affect the response to TMS. Among other sympathomimetic amines tested, it was seen that methamphetamine, ephedrine, phenylpropranolamine and mephentermine were effective in antagonizing DMPP-induced inhibition. High calcium (5 mM) reversed but did not prevent the DMPP-induced inhibition. DMPP reduced preferentially responses to high frequencies of stimulation without affecting those to low.