Chronic dopamine antagonism facilitates opiate-induced feeding.

Chronic interference with dopamine (DA) transmission has been found to facilitate opiate reward and opiate-induced behavioral activation derived from the nucleus accumbens. This study was aimed at determining the extent to which these effects are generalizable to opiate-induced feeding. Rats were tested for their feeding response to morphine following chronic interference with DAergic transmission with the long-acting neuroleptic, flupenthixol decanoate (FLU). It was found that FLU-treated animals showed an enhanced feeding response to morphine following three and four weeks of DA blockade, but not on weeks 1 and 2. Neither morphine treatment in FLU-control animals nor chronic FLU treatment alone produced any such time-dependent facilitation in feeding. The results indicate that the increased sensitivity to the rewarding effects of opiates following chronic DA blockade is generalizable to opiate-induced feeding.