Effects of apomorphine on appetitive conditioning in 6-hydroxydopamine treated rat pups

Rat pups were treated on postnatal day 5 either with the combination of desmethylimipramine (DMI) and 6-hydroxydopamine (6-OHDA) to produce depletion of brain dopamine, or with control injection of saline. Two days later they were presented a novel anise odor paired with intraoral baby formula, and on the next day were tested for preference for the novel odor. Before conditioning and testing, animals were treated with either apomorphine (0.05 mg/kg) or isotonic saline. Performance of the conditioned appetitive response was impaired in dopamine depleted animals. In DMI/6-OHDA treated pups, apomorphine administration prior to conditioning produced an improvement in performance, but drug treatment prior to testing had no effect. In normal pups, apomorphine administration either before conditioning or testing produced impaired performance at testing.