Sympathetic innervation of the porcine urethral muscle.

The striated perineal urethral muscle (UM) is involved in the voluntary control of the micturition that necessitates complex interactions between afferent and efferent (autonomic and somatic) pathways to store and periodically eliminate the urine. Our aim was to define the site, cross sectional area and phenotype of sympathetic trunk ganglia (STG) neurons projecting to the porcine UM, combining the retrograde neuronal tracer Fast Blue (FB) and the double immunohistochemical labeling. The research was carried out on 3 male intact pigs, in whichwecounted a totalnumberof 4992.67±834.35 (mean±S.E.M., n = 3) FB+ neurons distributed in the bilateral T12-S3 STG. These neurons were significantly larger in lumbar STG than the sacral ones. Moreover we highlighted the presence of Dopamine b hydroxylase (DbH), Vesicular Choline Acetyl Transferase (VAChT), neuronal Nitric Oxide Synthase (n- NOS), Calcitonin Gene Related Peptide (CGRP), Leu-Enkephaline(LENK), Neuropeptide Y (NPY), Substance P (SP), Vasoactive Intestinal Polypeptide (VIP) and Somatostatin (SOM) and their possible co-existence with Tyrosine Hydroxylase (TH) in both lumbar and sacral FB+ neurons. In particular lumbar and sacral STG neurons expressed similar percentages for TH, SP and CGRP, but showed significantly different levels of immunoreactivity for NPY, VIP, VAChT, LENK, nNOS, DbH and SOM. Taken together, these data indicate a probably different contribution of lumbar and sacral pathways in the sympathetic transmission to the boar UM.