Cholecystokinin in the central nervous system.

We have used high performance liquid chromatography and radioimmunoassay to characterize the CCK-like molecules in the central nervous system. The major form of CCK is the sulfated octapeptide. This molecule is distributed unevenly among various brain regions; the highest levels are found in the cortex and striatum. We have focused our attention on three areas in particular, the posterior pituitary, the caudate nucleus, and the hippocampus. The first of these receives its CCK-containing fibers from the hypothalamic magnocellular nuclei, the second appears to be innervated by the claustrum (or piriform cortex). The CCK in the hippocampus, on the other hand, is in intrinsic neurons. These structures and others in the brain have CCK binding sites.