Distribution and Nerve Pathways of Neurons Supplying the Bulbourethral Gland in the Pig

Abstract

The present study has disclosed for the first time the distribution and peripheral nerve pathways of autonomic and primary afferent neurons projecting to the bulbourethral gland (BG) in a mammalian species, the pig (n = 5), using combined retrograde tracing and cutting the hypogastric (n = 3) or pelvic (n = 3) nerve. Neurons projecting to the right BG were found in pelvic ganglia (PG), sympathetic chain ganglia (SChG; L2–S3), the caudal mesenteric ganglion (CaMG) and dorsal root ganglia (DRG; L1–L3, S1–S3). In general, the majority (about 75%) of them were located in the ipsilateral ganglia. Results of denervation experiments suggest that the neurons located in CaMG, and lumbar SChG and DRG project through the hypogastric nerve while processes of those found in the sacral SChG and DRG travel through the pelvic nerve or pelvic branch of the pudendal nerve. Moreover, the results obtained also suggest that the ‘crossing points’ (i.e. the areas where nerve fibres reach the opposite side) for the neurons found in the contralateral CaMG are located partly at the level of this ganglion and, for a smaller number of the nerve cells, at the level of the pelvic plexus. The crossing points for the SChG and DRG neurons are probably situated at the level of sympathetic chains and, for sacral SChG neurons, at the level of the pelvic plexus. The diversity of sources of the nerve supply to the porcine BG corresponds well with the variety (as previously distinguished with immunohistochemistry) of its intrinsic nerve fibre populations.