PREJUNCTIONAL AND POSTJUNCTIONAL EFFECTS OF N-ETHYLMALEIMIDE IN THE ISOLATED MOUSE VAS-DEFERENS

The influence of N-ethylmaleimide (NEM) on contractions due to exogenously applied noradrenaline and bethanechol and on the inhibitory effects of clonidine, of the enkephalin derivative, FK 33-824, and 2-chloroadenosine (2-CLA) on field stimulation-response curves and [3H]noradrenaline ([3H]NA) release was studied in the isolated mouse vas deferens. Exposure to NEM (60 μM: 10 min) caused a 30% reduction of the maximal contraction due to NA but nearly abolished the response to bethanechol. NEM partially reversed the depression of the pulse width-response curves the clonidine and FK 33-824 but was without effect with 2-CLA. The contractions evoked by stimulation frequencies above 20 Hz were depressed by NEM both in presence and absence of the agonists. NEM diminished the inhibition of the stimulation-evoked release of [3H]NA by the three agonists. The prejunctional effect of NEM was markedly influenced by the stimulation parameters. These findings support the suggestion that the inhibition mediated by α2-adrenoceptors, μ- and P1-receptors in the mouse vas deferens is NEM-sensitive and possibly transmitted by a pertussis toxin-sensitive G-protein. © 1990.