An immunohistochemical survey of peptide-containing nerves in the copulatory apparatus of several male birds

Abstract

Distribution of peptide-containing nerves in male copulatory apparatus as well as rectal and cloacal ganglia were examined immunohistochemically in cock, guinea fowl, duck and muscovy duck. Neurofilament protein-immunoreactive nerves were also examined to investigate general distribution of nerves. Substance P (SP)-, vasoactive intestinal polypeptide (VIP)-, calcitonin gene-related peptide (CGRP)-, and neuropeptide Y (NPY)-immunoreactive (IR) nerves were detected in al1 four species of birds whereas leucine enkephalin (LENK)-IR nerves were detected only in duck and muscovy duck. In the rectal and cloacal ganglia, peptide-IR nerves were detected in varying degrees of abundance. Most noticeable distribution was found in the vascular body, where SP-IR nerve fibres were more abundant in duck and muscovy duck, VIP-IR fibres in muscovy duck and CGRP-IR fibres in duck, than in other regions and other species, respectively. A few peptide-IR nerve fibres were detected in other cloacal regions, although a peculiar pattern in distribution unique to a certain region could be not found. The present results suggest that the peptidecontaining nerves participate in the regulation of tumescence, erection and detumescence of male copulatory apparatus of birds and their regulatory mechanisms are different depending on the species.