Intestinal infusion of a liquid diet alters CCK and NPY concentrations in specific brain areas of rats.

ABSTRACT

Cholecystokinin (CCK) and neuropeptide Y (NPY) have been implicated in the control of food intake in a number of species. This study was carried out to determine 1) whether nutrient-related stimulation of the upper small intestine could activate central CCK and NPY neuronal systems, resulting in changes in concentration of these peptides in specific brain areas, and 2) the influence of the circadian cycle on nutrient-related effects. Four groups of rats received treatments of either 1.0 ml saline (S) or Ensure liquid diet (E) infused into the duodenum either during the dark (D) or light (L) phase of the circadian cycle. CCK and NPY concentrations in extracts of specific brain areas were measured by RIAs. CCK concentration in the supraoptic n. (SON) was higher in D than in L, regardless of infusion treatment, and in the dorsal parabrachial n. area (DPN), CCK concentration was higher in E than S infused rats, regardless of circadian phase. CCK concentration in the dorsal motor vagal n. area (DMV) was higher in E, but only during L. NPY concentration was higher in DPN and paraventricular n. areas (PVN) and lower in the suprachiasmatic n. area (SC) after E, regardless of circadian phase. The changes in concentration of CCK and NPY in specific brain areas in response to food in the upper intestine suggest that nutrient-related signals from the intestine can activate specific CNS CCK and NPY-containing neural pathways.