Innervation of the striated muscle of the membranous urethra of the male dog.

Abstract

To identify the functional innervation of the striated muscle layer of the post-prostatic urethra of male dogs. Detailed anatomic dissection of the pelvic and pudendal nerves was carried out. The pressure and contractile responses to stimulation of these nerves were recorded in vivo and in vitro. Small branches of the pelvic nerve entered the membranous urethra but passed through the striated muscle to the inner smooth muscle layer. Stimulation of the nerve with 1 msec pulses at 10 Hz produced a slow contraction of the urethra which was unaffected by d-tubocurarine. Pudendal nerve branches entered the striated layer from the caudal end. Stimulation produced a rapid, visible contraction that was abolished by d-tubocurarine. Field stimulation of isolated strips of striated muscle resulted only in rapid, d-tubocurarine sensitive contractions. The striated muscle of the membranous urethra is innervated exclusively by the pudendal nerve.