Cholecystokinin acts on the hypothalamic "noradrenergic system" involved in feeding.

In male long Evans rats, microinjection cannulae were stereotaxically positioned to rest in sites in the preoptic area and medial hypothalamus. After the rats were satiated on wet mash, norepinephrine (NE) was infused in a dose of 2.5 micrograms and a volume of 0.75 microliter into these diencephalic sites. At loci in six animals, NE evoked spontaneous feeding of 5.0 gms or more of wet mash. Cholecystokinin (CCK) infused prior to the NE microinjection either intraperitoneally (0.5--1.0 microgram/kg) or at the NE-sensitive hypothalamic sites (75--150 ng) significantly attenuated or blocked the rat's feeding response to NE. The intake of water was unaffected by CCK in both instances. Thus, CCK may act on the diencephalic noradrenergic feeding system indirectly, through vagal afferent pathways, or directly within the animal's hypothalamus.