Profound changes in intestinal motility occur during the postnatal period but the involvement of the enteric nervous system (ENS), a key regulator of gastrointestinal motility (GI), in these modifications remains largely unknown. We therefore investigated the postnatal development of the ENS phenotype and determined its functional repercussion upon the neuromuscular transmission in the rat colon. Sprague Dawleys rats were sacrificed at postnatal day 1 (P1), P3, P5, P7, P14, P21 and P36. Whole mounts of colonic myenteric plexus were stained with antibodies against choline acetyltransferase (ChAT), neuronal nitric oxide synthase (nNOS) and HuC/D. Colonic contractile response induced by electrical field stimulation (EFS) was investigated in organ chambers in absence or presence of L-NAME and/or atropine. In vivo motility was assessed by measurement of the colonic bead latency time. Randomly occurring ex vivo contractions appeared starting P5. Starting P14, rhythmic phasic contractions occurred whose frequency and amplitude increased over time. In vivo, bead latency was significantly reduced between P14 and P21. Ex vivo, EFS-induced contractile responses increased significantly over time and were significantly reduced by atropine starting P14 but were sensitive to L-NAME only after P21. The proportion of ChAT-immunoreactive (IR) neurons increased time dependently starting P14. The proportion of nNOS-IR neurons increased as early as P5 as compared to P1 but did not change afterwards. Our data support a key role for cholinergic myenteric pathways in the development of postnatal motility and further identify them as putative therapeutic target for the treatment of GI motility disorders in the newborn.
- postnatal development
- enteric nervous system
- myenteric plexus
- Copyright © 2010, American Journal of Physiology- Gastrointestinal and Liver Physiology