POSTNATAL-DEVELOPMENT OF THE AUTONOMIC AND SENSORY INNERVATION OF THEMUSCULATURE IN THE RAT URINARY-BLADDER

The postnatal development of the innervation of the muscle layer in th e rat urinary bladder was analysed in whole mount preparations using i mmunohistochemistry against protein gene-product 9.5 (PGP; general neu ronal marker), growth-associated protein 43 (GAP), dopamine p-hydroxyl ase (DBH), neuropeptide Y (NPY), vasoactive intestinal polypeptide (VI P), calcitonin gene-related peptide (CGRP) and substance P (SP). Immun oreactive nerve fibres for all markers were already present at birth. The density of PGP- and GAP-positive nerve fibres was similar and rema ined constant throughout the postnatal development. The rank order of densities for the other markers relative to PGP was NPY (129-189%) > C GRP (20-63%)> SP (7-23%) > DBH (7-12%) > VIP (2-11%). While the densit y of presumably efferent VIP-and DBH-positive fibres did not change po stnatally, NPY-positive fibres reached adult density at the fifth post natal day. Sensory CGRP-and SP-positive nerve fibres approached adult levels at the end of the second week, shortly before the micturition r eflex was completely developed. The data suggest that a sufficient rel ative density of sensory and certain efferent elements might be a prer equisite for the development of the mature micturition reflex. (C) 199 7 Elsevier Science Ireland Ltd.