Immunocytochemical demonstration of PHI and its co-existence with VIP in intestinal nerves of the rat and pig.

Immunocytochemical studies of the rat and pig indicate that immunoreactivity for PHI (heptacosapeptide recently isolated by TATEMOTO and MUTT, 1981, from the porcine intestine) is located in numerous nerve fibers in the ileum and colon. Myenteric and submucosal plexuses contain abundant PHI-immunoreactive fibers. Alternate staining of adjacent sections with anti-PHI and anti-VIP sera indicates that PHI-immunoreactive nerves coincide with VIP nerves. This co-existence of both peptides in the same neurons may be accounted for by their probable sharing of a common precursor.