Cholecystokinin octapeptide like immunoreactivity: Histochemical localization in rat brain

Cholecystokinin octapeptide-like (CCK-OP-like) immunofluorescence method.Specificity in immunohistochemical studies was demonstrated by the virtual elimination of staining with either preimmune sera or sera preadsorbed with CCK-OP and by the achievement of similar fluorescent patterns with two different primary anti-CCK-OP sera. CCK-OP-like fluorescence was localized in neuronal cell bodies, fibers, and various terminals. The most dense collections of CCK-OP cells occurred in the periaqueductal gray and in the dorsomedial hypothalamus. substantial numbers of cells and fibers were present in the medial/dorsal and perirhinal cortex; more limited groups of cells were found in the pyramidal layer of the hippocampus and in the dorsal raphe.