Pharmacological studies on supersensitization. II. Specificity of drug-induced supersensitivity of isolated vas deferens of rat (author's transl)

Abstract

Dose-response relationship of potentiation of contractile response of isolated vas deferens of a rat to norepinephrine (norepi) and acetylcholine (ACh) by seven potentiators, including cocaine, tripelennamine, diphenhydramine, and phentolamine, were examined. The maximum response of epididymal portion of vas deferens to both agonists was greater than that of prostatic portion and the degree of increase in maximum response induced by the potentiators was in reverse relation to the degree of maximum response. Potentiators increased the maximum response of vas deferens to norepi and ACh up to the same level of maximum response induced by transmural electrical stimulation, which was estimated to be the mechanical limit of contracture. The mechanism of increase in sensitivity and that in maximum response to norepi seemed to be different, but linear relation between increase in sensitivity and that in maximum response to ACh was recognized. Linear relation was also recognized between increase in maximum response to norepi and ACh. Dibenamine inhibited the increase in sensitivity of vas deferens to ACh by cocaine selectively. From these results, the supersensitization of vas deferens of a rat was classified into four groups : (1) Presynaptic catecholamine potentiation, (2) Dibenaminesensitive cocaine-induced supersensitivity, to ACh, (3) Dibenamine-insensitive supersensitivity to ACh, and (4) The so-called nonspecific increase in maximum response to norepi and ACh.