FOOD FOR THOUGHT - A CRITIQUE ON THE HYPOTHESIS THAT ENDOGENOUS CHOLECYSTOKININ ACTS AS A PHYSIOLOGICAL SATIETY FACTOR

This review evaluates the various lines of evidence supporting the.hyp othesis that cholecystokinin (CCK) released from the small intestine d uring feeding plays a physiological role in mediating satiety. Issues considered include, the effects of systemic injection oi CCK on consum matory and operant Feeding, the role of the vagus nerve, the effects o f CCKA and CCKB receptor antagonists, and the neuroendocrine responses to exogenous CCK. A critical appraisal of this research indicates tha t while it is clearly demonstratable that exogenous peripheral CCK can alter food intake by acting on CCKA receptors, the mechanism involved may be more closely related to the induction of aversion and nausea, rather than satiety. With regard to peripheral endogenous CCK, the ava ilable evidence also does not seem to support a role for the hormone i n satiety. In particular, it is doubtful whether plasma concentrations of CCK Following a meal are sufficiently high to inhibit feeding. Mor eover, CCKA receptor antagonists which do nor cross the blood brain ba rrier fail to increase meal size, as would be expected if peripheral C CK was an effective satiety factor. In addition, the recent literature concerned with the possibility that CCK may have a direct action with in the brain in the control of food intake has been reviewed. These st udies show that CCK adminstered intracerebroventicularly, or by micoin jection into discrete brain regions, also inhibits feeding via a CCKA receptor mechanism. However, the physiological relevance of these find ings have yet to be determined. (C) 1998 Elsevier Science Ltd. All rig hts reserved.