OPPOSITE INFLUENCE OF CARBOHYDRATES AND FAT ON HYPOTHALAMIC NEUROTENSIN IN LONG-EVANS RATS

Neurotensin inhibits food intake when injected in the central nervous system and is released after fat ingestion. The aim of the present stu dy was to measure it in different brain areas and to determine if it i s involved in the long-term variations in food intake induced by the i ngestion of a high-fat (HF) diet. We compared the results with those o btained with 2 low-fat [high-carbohydrates (HC)] diets and a well-bala nced diet. For this purpose, weanling male Long-Evans rats were fed ad libitum for 14 weeks either on a control diet, a HF diet or a HC diet . The rats with the HC (high-starch) diet were divided into 2 subgroup s: the first (HC) drank water and the second (HCS) drank a 25% sucrose solution. During the last week of the experiment, energy intake of th e HCS rats was significantly greater than that of the 3 other groups o f rats (+ 17.2%; p<0.01; + 27.1%; p<0.001 and + 34.6%; p<0.001 vs the control, HC and HF rats respectively). NT did not vary in the midbrain and particularly in the ventral tegmental area. Its concentrations we re significantly higher in the 2 HC groups than in the HF rats both in the paraventricular (PVN; p<0.02) and dorsomedial nuclei (DMN; p<0.03 ). In the DMN, they were positively correlated with energy intake (r=0 .39; p=0.027). These results indicate that hypothalamic neurotensin is indeed involved in the long-term modulation of feeding behavior by di et composition and that fat is the more potent macronutrient for its r egulation.