Evoked release of [14C]norepinephrine from the rat hypothalamus during feeding

The pattern of catecholamine release was studied at sites adjacent to the lateral ventricle or in the anterior, dorsomedial or ventromedial hypothalamus of the rat as it was feeding. Endogenous stores of norepinephrine (NE) were first labeled by the microinjection of [14C]NE into these circumscribed sites. Subsequently, [14C]NE release was examined by repeated perfusions of an artificial cerebrospinal fluid through a push-pull cannula at the rate of 23 mul/min for 5-10 min every 30 min. After successive control perfusates were collected, food or water was given to the animal. During an interval of feeding, a significant efflux of [14C]NE and its metabolites occurred reliably from midline structures of the hypothalamus at the level of the ventromedial nucleus. Although the feeding-related output of [14C]NE detected within the anterior hypothalamus was lower, [14C]NE was also released from this region when the rat pressed a lever to obtain food pellets. These results support the view that endogenous catecholamines underlie, at least partially, diencephalic mechanisms controlling food intake, including sensory, motor, or motivational components.