Distribution of VIP-immunoreactive nerve cells and fibers in the human ileocecal region.

VIP-containing nerve cells and fibers in the human ileocecal region (pre-junctional ileum, ileocecal and cecocolonic junctions, post-junctional cecum and colon) have been evaluated by immunocytochemistry. A high density of VIP-positive neurons and nerve fibers was found in all layers of the ileum. At all colonic levels examined and at both junctions, the percentage of VIP-containing cells was higher in the submucous plexus than in the myenteric plexus. At both junctions, the muscle wall was devoid of, and the myenteric plexus extremely poor in VIP-positive nerve fibers and cells. These data suggest that motility of these junctions is not--or only to a minor extent--regulated in man by VIP-containing nerves, at variance with other gut sphincteric areas.