Pharmacological study of autonomic innervation of dog retractor penis

Abstract

Transmural stimulation of the dog retractor penis in vitro produced a rapid contraction which was blocked by bretyl-ium, guanethidine, local anesthetics, and adrenolytics, but not by hexa-methonium or hemicholinium. Bretylium and guanethidine produced a gradually developing contraction. Electrical stimulation of the bretyl-ium-contracted muscle produced relaxation which was inhibited by local anesthetics but not by atropine or scopolamine; it was not potentiated by eserine. Acetylcholine in high concentrations produced contractions blocked by atropine; it did not inhibit the contracted muscle. ([long dash])-Dichloroisoproterenol blocked the inhibitory effect of ([long dash])-iso-proterenol on the dog retractor penis both in vivo and in vitro but did not alter the inhibitory effect of the pelvic nerve or the relaxation induced by transmural stimulation (bretylium-treated preparation). The contraction produced by transmural stimulation is due to activation of postganglionic sympathetic fibers and that the relaxation which follows the transmural stimulation of the bretylium-treated muscle is due to activation of noncholinergic postganglionic parasympathetic fibers.