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Lesions of the Ventral Tegmental Area Disrupt Drug-induced Appetite Stimulating Effects but Spare Reward Comparison

  • Author(s): Twining, Robert C.
  • Hajnal, Andras
  • Han, Li
  • Bruno, Kristy
  • Hess, Ellen J.
  • Grigson, Patricia S.
  • et al.
Abstract

Dopamine neurons in the ventral tegmental area (VTA) - nucleus accumbens (NAC) pathway track both absolute and relative properties of reward. The present study used 6-hydroxydopamine lesions of the VTA to test the obligate role of this nucleus in morphine- and cocaine-induced suppression of conditioned stimulus (CS) intake and in chlordiazepoxide- and morphine-induced appetite stimulating effects. The results showed that an 80% reduction in accumbens DA fully prevented drug-induced appetite stimulating effects, augmented a latent inhibition-like effect, but failed to disrupt druginduced suppression of CS intake. These data demonstrate that, while the VTA is essential for responding to the reward-enhancing effects of chlordiazepoxide and morphine, it does not contribute to cocaine- or morphine-induced devaluation of the lesser saccharin reward cue.

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