DISTRIBUTION OF NEUROPEPTIDE-OXIDE, TYROSINE HYDROXYLASE-OXIDE AND NITRIC-OXIDE SYNTHASE CONTAINING NERVE-FIBERS IN THE EXTERNAL URETHRAL SPHINCTER OF THE RAT

The occurrence and distribution of adrenergic, peptidergic and nitrerg ic nerve fibers were investigated within the part of the rat urethra t hat corresponds to the external urethral sphincteric mechanism. At thi s level, the urethral wall was found to be composed of the following l ayers: mucosa/urothelium, lamina propria, smooth muscle, mixed smooth and striated muscle and striated muscle. Nerve fibers containing immun oreactivity against either nitric oxide synthase (NOS) or any of the f ollowing peptides Mere visualised in various amounts in all three musc le layers of rats of both sexes: neuropeptide Y (NPY), vasoactive inte stinal polypeptide (VIP), calcitonin gene related peptide (CGRP), subs tance P (SP), cholecystokinin (CCK), gastrin releasing peptide (GRP) a nd pituitary adenylate cyclase-activating peptide (PACAP). Tyrosine hy droxylase (TH), marker for noradrenergic nerves, was only found in ner ve fibers of the smooth and mixed muscle layers, while enkephalin-8 (E NK-8) was only found in the striated muscle layer. The great number of putative neuromessengers and different nerve fiber populations sugges t a complex innervation pattern of the sphincter area.