Difference between inhibitory actions of papaverine and dehydroepiandrosterone on the isolated guinea-pig ileum

Dehydroepiandrosterone (DEA), a metabolite of steroid hormone in the urine, differed from papaverine in the mode of inhibitory action on the isolated guinea-pig ileum. Papaverine inhibited both phasic and tonic contractions induced by an agonist, while DEA inhibited the phasic contraction without apparent fatigue of the tonic phase. The main action of papaverine seems to be predominatly a metabolic inhibition similar to that of metabolic inhibitors, but the action of DEA could not be ascribed to that of metabolic inhibition. In the presence of papaverine or metabolic inhibitors the height of maximal contraction of an agonist tested by the cumulative method was greatly depressed and less than that by a single method. The longer the time involved in the cumulative doses, the lower was the maximal contraction.