Norepinephrine uptake by hypothalamic tissue from the rat related to feeding

Norepinephrine (NE) uptake by rat hypothalamus in vitro was studied in relation to food intake. Significant daily variations in NE uptake were observed in caudal hypothalamus from freely feeding rats. A maximal elevation occurred at the beginning of the night when food intake is also increasing to a maximum. NE uptake by caudal hypothalamus from relatively hungry rats previously adjusted to restricted feeding during the daytime was enhanced in afternoon and evening when compared with uptake by tissue from ad lib feeding animals. Determination of NE uptake by caudal hypothalamus from freely feeding individual rats and registration of individual meals taken by these rats revealed a relation between hypothalamic neuronal activity and the feeding pattern of the rat. A positive correlation was observed between NE uptake in vitro and feeding rate during a 2- to 4-hr interval. It also appeared that NE uptake by caudal hypothalamus is dependent on the time elapsed after the last meal. The data were evaluated in view of physiological studies concerning the onset of feeding and the hypothesis of hypothalamic adrenergic control of food intake.