VIP-innervation of rat intestine: a developmental study with monoclonal antibodies.

Four monoclonal antibodies to VIP have been generated and shown to be N-terminal specific with high affinity for VIP. VIP-containing nerve fibers and cell bodies were visible in the upper small intestine from day 1 of neonatal life. Initially the immunoreactivity was mostly in the myenteric plexus but extended into the sub-mucous plexus by day 7. From day 1 to day 7 the VIP-innervation developed both orally and caudally at a similar rate. In the stomach, the antrum showed sub-mucosal cell bodies by day 14, while in the corpus the cell bodies remained confined to the myenteric plexus. The colon showed positive fibers in the myenteric plexus at day 7 and cell bodies and fibers in the sub-mucous plexus by day 14. The size (cross-sectional area) of the individual VIP-immunoreactive cell bodies increased significantly between day 1 and day 14 with no further increase with age. At no time were immunoreactive cell bodies shown to migrate from the myenteric to the sub-mucous plexus. VIP-immunoreactive epithelial cells were not detected in the present study.