NEUROTRANSMITTERS IN THE HUMAN URETHRAL SPHINCTER IN THE ABSENCE OF VOIDING DYSFUNCTION

The purpose of this study was to elucidate the neuroregulation of sphi ncteric relaxation by investigating the density of nerves containing a cetylcholine, noradrenaline, neuropeptide Y (NPY), galanin, vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGR P) in the urethral sphincter in patients without a voiding disorder. T he complete urethral sphincter (from the bladder neck to beyond the st riated external sphincter) was excised from four male and four female adult cadavers and one male and one female fetus. In transverse paraff in or cryostat sections, the above transmitters were identified by his tochemical methods. The striated sphincter was densely innervated by c holinergic nerves. Adrenergic nerves next to striated fibers were rare , but were present in all patients. NPY was seen rarely along striated fibers. In the smooth sphincteric component, noradrenaline-, acetylch oline-, NPY- and galanin-reactive nerves were observed frequently. Onl y functional studies can clarify the clinical implications of these re sults. Judging from NPY's scarcity in the striated sphincter no effere nt function is anticipated. In the smooth component the frequent appea rance of NPY, galanin and noradrenaline suggests a regulatory role for these transmitters.