Neuropeptidergic innervation of the human male distal urethra and intrinsic external urethral sphincter.

The innervation of the human male distal urethra and intrinsic external urethral sphincter was investigated by immunohistochemical techniques. The innervation density was low. In the urethra neuropeptide, and vasoactive intestinal polypeptide positive nerves were found in the muscular layer, calcitonin gene-related peptide, galanin and PHI nerves were localized in the epithelium. In the intrinsic external urethral sphincter NPY and galanin nerves were quite numerous between the striated muscle bundles, calcitonin gene-related peptide, vasoactive intestinal polypeptide and PHI were only seen occasionally as thin fibres.