Characterization of the impaired feeding behavior in rats given haloperidol or dopamine-depleting brain lesions.

Systemic administration of 0.2 mg/kg of the dopamine antagonist haloperidol reduced the rate of feeding in food-deprived rats, whereas a dose of 0.4 mg/kg suppressed both the rate of feeding and time spent feeding. Pre-feeding a group of rats decreased the time spent feeding but had minimal effects on the rate of feeding. Regression analysis showed that food intake, time spent feeding, and rate of feeding were related to each other in different ways in haloperidol-treated and pre-fed rats. Near-total depletion of brain dopamine by injection of the neurotoxin 6-hydroxydopamine into the medial forebrain bundle initially decreased both time spent feeding and feeding rate. When rats that were initially aphagic after dopamine depletion recovered feeding behavior, their rate of feeding did not return to control values, and they spent more time feeding than control rats. Similarly, 6-hydroxydopamine-treated rats with smaller dopamine depletions, which were not initially aphagic after the lesions, nevertheless had a prolonged reduction in the rate of feeding. Although control rats typically held the food pellets in both forepaws while feeding, dopamine-depleted rats often fed with one or no paws holding the pellet. The suppression of food intake and rate of feeding in 6-hydroxydopamine-treated rats was correlated with the depletion of dopamine in the lateral striatum, but not the medial striatum. These results indicate that dopamine in the striatum is involved in aspects of motor control that are necessary for efficient feeding behavior in rats.