Effects of Several Autonomic Drugs on the Responses of the Isolated Rabbit Detrusor Muscle Strips to Electrical Stimulation

Rim, Joung Sik; Min, Byung Kap

Abstract

Effects of several autonomic drugs on the responses of the isolated rabbit detrusor muscle strips to electrical stimulation were investigated. Electric stimulation of the detrusor muscle strips elicited two different responses; (a) contraction followed by relaxation in 14 cases out of 22 experiments, and (b) contraction only in 8 cases. The contraction responses to electrical stimulation were significantly reduced in the presence of either atropine or regitine, respectively The relaxation response to electrical stimulation was abolished in the presence of propranolol. Addition of norepinephrine evoked one of following three responses: (a) relaxation in 10 cases out of 19 experiments, (b) contraction in 6 cases, and (c) contraction followed by relaxation in 4 cases. The relaxation response to norepinephrine was reversed. in the presence of propranolol, to a contraction response which was then abolished after administration of regitine. The contraction response to norepinephrine was reversed, in the presence of regitine, to a relaxation response which was then abolished after administration of propranolol. Acetylcholine elicited contraction of the isolated detrusor muscle strip, and this was abolished in the presence of atropine These results suggest that the rabbit detrusor muscle is innervated by both cholinergic and adrenergic fibers and that the detrusor muscle contains cholinergic receptors as well as adrenergic a-and b-ones. Contrary to the popular opinion that the detrusor muscle predominantly contains adrenergic b-receptors, it seems likely that the adrenergic receptors differ in predominancy of either a or b which elicits contraction or relaxation, respectively, according to different areas of the muscle.