The development of motilin, cholecystokinin and vasoactive intestinal peptide immunoreactivity in the forebrain and hindbrain of the rat, as determined by radioimmunoassay.

Forebrain and brainstem motilin, cholecystokinin (CCK) and vasoactive intestinal peptide (VIP) were determined in rats from 4 days before to birth to 180 days after. CCK and VIP develop postnatally, as previously reported. Motillin concentrations in both areas, however, were highest 4 days before birth, decreasing after birth. In the oldest animals, motilin, CCK and VIP levels were decreased. The presence of substantial motilin immunoreactivity in the brain before birth is suggestive of a possible role for motillin in the regulation of development.