ELECTROPHYSIOLOGICAL EVIDENCE FOR THE NOMENCLATURE OF THE PUDENDAL NERVE AND SACRAL PLEXUS IN THE MALE-RAT

Surgical microscopy and electrophysiological techniques were used to s tandardize the nomenclature for the pudendal nerve and sacral plexus a ccording to their somatic axonal composition in the male rat. We concl ude that the pudendal nerve is the segment running from the L-6-S-1 tr unk to the sacral plexus, carrying efferent fibers to the coccygeus, i nternal obturator, ventral and dorsal bulbospongiosus, ischiocavernosu s, external anal sphincter, and external urethral sphincter muscles, a nd afferent fibers from the penis, prepuce, scrotum, and ventral-proxi mal tail. The sacral plexus is the complex formed by the bridge-like s tructure connecting the pudendal nerve with the lumbosacral trunk, and two nerve branches emerging from it, one innervating the proximal hal f of the scrotal skin, and the other innervating the muscles at the ba se of the penis known as the motor branch. These branches are only con sidered as a part of the sacral plexus because they integrate axons fr om both the lumbosacral trunk and pudendal nerve. The gross anatomy of the pudendal nerve and sacral plexus has a main organization that was observed in 70% of cases, whereas the remaining 30% occurred in two v ariants. This nomenclature is appropriate to describe the pudendal ner ve and sacral plexus in studies that involve them being lesioned or el ectrophysiologically analysed. A main additional finding was that two large afferent branches innervate the scrotum, one the proximal half a nd the other the distal half. As mentioned above, the proximal branch belongs to the sacral plexus, whereas the distal branch belongs to the pudendal nerve because all its axons travel to the cord via this nerv e. Since stimulation or even manipulation of the scrotal branches resu lted in the secretion of semen containing spermatozoa, it is suggested that scrotal afferents are involved in some way in the ejaculatory pr ocess, a topic that deserves further research. (C) 1997 Elsevier Scien ce B.V.