Observations on the structure and autonomic innervation of the guinea-pig seminal vesicle and ductus deferens.

A combination of light microscopic, neurohistochemical and electron microscopic techniques were used to study the distribution of autonomic nerves in the seminal vesicle, and in the submucosa of the ductus deferens, in the guinea-pig. In routine histological preparations, the muscle coat of the seminal vesicle consisted largely of circularly orientated smooth muscle cells with an additional longitudinal layer confined to its urethral end. Using fluorescence microscopy, a rich plexus of noradrenergic nerves was demonstrated throughout the muscle coat of the seminal vesicle and this was confirmed electron microscopically. Numerous noradrenergic terminal regions were frequently observed 10-100 nm from adjacent smooth muscle cells, and catecholamine-containing nerve cell bodies were observed in the adventitia of the urethral end of the seminal vesicle. With the light microscope, a rich plexus of AChE+ve nerves was found in the circular muscle layer but the outer longitudinal layer contained few similar nerves. AChE+ve ganglion cells were confined to the adventitia of the urethral end of the seminal vesicle. Electron microscopy revealed a second type of terminal region containing small agranular vesicles, the distribution of which corresponded to that of the AChE+ve nerves observed by light microscopy. In both layers, these terminal regions were associated with other axons, although the circular muscle layer also contained single axons of this type in close association with adjacent smooth muscle cells. Very few noradrenergic nerves were found in the submucosa of the seminal vesicle and ductus deferens and those which were observed usually accompanied the vascular supply. In contrast, a rich AChE+ve nerve network was observed in the submucosa of both the seminal vesicle and the ductus deferens. Electron microscopy revealed numerous groups of submucosal axons, many of which appeared varicose and contained small, agranular vesicles. Similar intra-epithelial axons were occasionally observed in both organs. These findings have been discussed in relation to the possible functional significance of this extensive autonomic innervation.