Effect of Phenobarbital Pretreatment on the Sensitivity of the Isolated Guinea Pig Vas Deferens to Various Agonists

Abstract

The influence of phenobarbital pretreatment was studied on the sensitivity of the isolated guinea pig vas deferens to various agonists. The results reported in this communication show that such pretreatment produces an unspecific supersensitivity to catecholamines, histamine, and acetylcholine. Furthermore, the anticholinergic actions of atropine, the antihistaminic action of diphenhydramine, and the α-blocking property of phentolamine are reduced by the phenobarbital pretreatment. In conclusion, it is proposed that the supersensitivity observed is of the postsynaptic type and probably related to the facilitation of the energetic process involved in the smooth muscle contraction.