Similar effects of D(1)/D(2) receptor blockade on feeding and locomotor behavior.

Recent evidence suggests an important relationship between dopamine (DA) modulation of feeding and locomotor activity. To investigate this relationship, the free-feeding and locomotor behavior of rats under the influence of D(1)/D(2) antagonist cis-flupenthixol was examined. DA antagonists are known to produce within-session declines in reinforced behavior, with behavioral suppression occurring only after a number of normal responses have been emitted. In the present study, cis-flupenthixol (0.30 mg/kg ) produced a within-session decrement in both free-feeding behavior and in locomotor/exploratory activity of animals in an environment that had never been paired with food. In addition to producing similar patterns of disruption in feeding and locomotion, the drug also produced a similar magnitude of suppression in the two behaviors. The results show that disruption of DA activity suppresses locomotor/exploratory activity in a manner that closely mirrors neuroleptic suppression of feeding. Although neuroleptic-induced suppression of locomotion and feeding are traditionally presumed to reflect an attenuation of DA motor and reward functions, respectively, the present results suggest that DA plays a similar role in the modulation of these two behaviors.