Central nervous system cholecystokinin and the control of feeding

There is still much to learn of the sites and mechanisms of action of brain CCK peptides and their interaction with other brain peptides and neurotransmitters. The findings obtained from studies in sheep and other species provide evidence for brain CCK peptides functioning as important transmitters of hunger and satiety signals. We have hypothesized that signals, either neural or humoral, peripherally generated as a result of feeding induce secretion of CCK from specific (paraventricular) brain sites into the CSF (FIG. 1). Specialized ependymal cells, such as tanycytes, may take up CCK from the CSF for transport to receptor sites which mediate CCK's specific functions (such as changes in rumen motility, suppression of insulin secretion, and behavioral satiety). Evidence also exists to indicate the involvement of specific hypothalamic sites in either the release or the action of CCK.