Ontogeny of neuropeptides in the rat urinary bladder

Urinary bladders of male rats at ages ranging from 1 day to 18 months were analysed for their neuropeptide content. NPY was detected at birth, VIP and CGRP at 1 week, and SP at 2 weeks. There was then a sharp increase in both the total amounts and concentrations of VIP, CGRP and SP until the rats had reached the age of 3-4 weeks. The total amount of NPY increased in two surges, between 2-3 weeks and between 4-5 weeks. The concentration of NPY showed a biphasic course, a decrease during the first two weeks and then an increase. In adults the total amounts of substance P and CGRP were higher than in younger animals, whereas that of VIP was lower. Following peaks at 3-8 weeks, the concentrations of VIP and substance P decreased with age, whereas that of CGRP remained unchanged. NPY was not followed beyond 8 weeks. The present findings offer a framework for future studies aimed at elucidating the functional role of neuropeptides in the regulation of micturition.