Specimens of testis, excurrent duct including the accessory genital glands and urethra throughout its extension were investigated in adult bovines, in order to imm~~nohistochemicalllyo calize both the peptidergic innervation and the epithelial cell types belonging to [he diffuse endocrine system (DES). Immunoreactivities to GRP, met- and leu-enkephalins, CGRP, NPY, substance P, VIP, somatostatin, l3-endorphin and 5-HT antisera were tested by means of a labelled streptavidin-biotin (LSAB) method. Such regulatory substances were found in components of the peripheral nervous system (nerve fibers in the connective and muscular tissues, sub- and intraepithelial nerve terminals, nerve cell bodies and fibers in intramural ganglia), and in epithelia1 endocrine/ paracrine cells. Bovine urogenital apparatus is supplied by many peptide-containing nerves, which contain in many localizations GRP and enkephalins, and to a lesser extent substance P, CGRP, NPY and VIP. A thin network of peptidergic nerves distributes to the musculature of the canalicular organs and accessory glands. The prostatic complex was especially rich in peptidergic innervation, and also contained somatostatin- and 5-HTsecreting endocrine cells. In addition, 5-HT-immunoreactive endocrine cells were found in the bulbourethral gland and urethral epithelium. CGRP-ir nerves were present contacting striated muscle fibers of urethra (motor end plates). The testis was devoid of any immunoreactivity. These data are compared with those obtained in a companion study carried out the same organs in two species of Equidae (Equus caballus and Equus asinus). Different patterns of immunoreactivities can be outlined in these domestic ungulates
