Distinct effects of anterior pyriform cortex and the lateral hypothalamus lesions on protein intake in rats

Several specific locations in brain, including pyriform cortex and hypothalamus, are associated with regulation of food intake. Although lesions of these locations significantly alter food intake, their involvement in the selection of macronutrients is not well characterized. In this study, we examined distinct effects of anterior pyriform cortex (APC) and lateral hypothalamus (LH) lesions on protein intake in rats. The APC or LH of male adult rats were lesioned by treatment with kainic acid, and the rats were then given free access to two kinds of casein diets containing high (60%) and low (5%) protein. Total energy content of these diets was kept constant by changing the carbohydrate content. Following the APC lesions, body weight and food intake decreased, but returned to control levels on day 13 and day 4, respectively. APC lesions did not change the ratio of protein intake. In contrast, LH lesions disturbed body weight gain and the selection of a high protein diet for at least two weeks, although food intake returned to control levels by day 2. Our results suggest that LH, but not APC, may play an important role in the selection of protein intake in rats.