Release of endogenous catecholamines from rat hypothalamus in vivo related to feeding and other behaviors

The release of endogenous noradrenaline (NA) and dopamine (DA) from various sites in the hypothalamus was determined in unanesthetized, freely moving rats by means of a push-pull perfusion technique in combination with a sensitive radiochemical assay. The perfusate was collected continuosly over 10-min periods for 4 to 8 hr. Patterns of feeding, drinking, grooming, and locomotor activity were recorded during the perfusion experiments. Release patterns and behavior recordings were analysed by tests of serial correlation. Although significant variations in catecholamine release over time were observed, they did not reflect a fixed autonomic periodicity. Release from the medial hypothalamus was measured in rats which had been deprived of food for 16 hr and were subsequently given free access to food. Before food presentation, mean NA release over 10-min periods was consistently higher than during satiety. Mean NA and DA release over 10-min periods before, during and after the occurence of feeding, drinking or grooming were calculated for the dorsomedial, perifornical, subfornical, and anterolateral hypothalamus of freely feeding rats. During feeding, NA (but not DA) release from the dorsomedial and perifornical areas was significantly elevated (40–50%) when compared with pre- or postfeeding values. An increase in catecholamine release was not observed during drinking or grooming. In addition, NA release from the anterolateral area correlated with locomotor activity. The enhancement of NA release from the perifornical area during feeding is considered to be specific as no change in release was observed even during the drinking vigorous response induced by angiotensin.