CGRP innervation and receptors during aging of male and female hepatic rat portal veins.

Calcitonin gene-related peptide (CGRP) innervation and binding sites were studied on hepatic portal veins of male and female rats from 19 days to 22 months of age. CGRP containing nerve fibers were present both in adventitial and medial nerve plexuses, closely apposing to or penetrating into the muscular layers. The density of CGRP innervation was estimated on whole mount preparations and compared during aging. In females, aging did not affect the number of fibers per unit length, although the vessel circumference decreased after 6 months of age. In males, the vessel circumference remained constant during aging, while the density of innervation significantly decreased. Whatever the age or sex of the animals was, no CGRP binding sites were found on portal veins sections by autoradiography. CGRP had no effect on spontaneous contractions of perfused portal veins. The difference observed in the evolution of CGRP innervation density between males and females suggests that CGRP innervation in the rat portal vein may be influenced by gonadal steroids during aging.