Dopamine efflux from the brain stem of the rat during feeding, drinking and lever-pressing for food.

To determine whether endogenous dopamine (DA) is involved in the control of feeding and drinking, the cerebral activity of 14C-DA was examined in the rat while the animal consumed food or water. A push-pull guide tube was implanted above sites either adjacent to the third ventricle, the anterior hypothalamus or the substantia nigra in each of 41 rats. After the endogenous stores of DA at specific sites were labelled by a microinjection of 0.5 to 2.0 muCi of 14C-DA, an artificial CSF was perfused at half-hour intervals at a rate of 20-23 mul/min in these sites in the food deprived rat. After a 14C-washout curve of radioactivity in the perfusate was derived for successive control samples, the food-deprived rat was offered food or water which was ingested during the course of one or more perfusions. As the rat consumed food, 14C-DA was released in some experiments from circumscribed sites in the nucleus reuniens and the zona incerta. The efflux of 14C-DA from certain sites in the circumscribed sites in the nucleus reuniens and the zona incerta. The efflux of 14C-DA from certain sites in the ventromedial and dorsomedial hypothalamus as well as from the substantia nigra also was enhanced as the rat depressed a lever to obtain food pellets. Since 14C-DA was also released from the zona incerta, perifornical hypothalamus, and into the third ventricle as the rat drank water, these results suggest that dopaminergic neurons in the brain stem play some part in the motor component of ingestive behavior rather than feeding per se.