Ontogeny of cholecystokinin-immunoreactive structures in the primate cerebral neocortex.

Distribution of cholecystokinin (CCK)-immunoreactive structures was studied in various neocortical areas of macaque monkeys during prenatal and postnatal development. The largest number of CCK-immunoreactive cells was observed at embryonic day 140, and subsequently they decreased in number until postnatal day 60. A few cells which were presumably degenerated neurons were observed during postnatal development. A higher density of CCK-immunoreactive cells was observed in the supragranular layers (layers II and III) than in the infragranular layers (layers V and VI). The number of CCK-immunoreactive cells was larger and changed more conspicuously in the association areas than in the other areas during development. In contrast, in the occipital area, the number of such cells was small and changed only a little. These findings suggest that CCK may be involved in the development and special function of each neocortical areas of the primate.