A selective role for dopamine in the nucleus accumbens of the rat in random foraging but not delayed spatial win-shift-based foraging

The role of mesoaccumbens dopamine (DA) in radial-arm maze foraging is assessed by infusing low doses of the DA antagonist haloperidol into the nucleus accumbens (N.Acc.). Infusions of haloperidol (0, 125, 250 or 500 ng/0.5 mu l) into the N.Acc. of well-trained rats dose-dependently increase the number of re-entries to arms (errors) during the random foraging task, in which 4 arms on an 8-arm maze are baited randomly. However, in a separate group of animals, similar infusions produce no impairment when delivered prior to the test phase of the delayed spatial win-shift task, which require the animal to acquire information during a training phase, and to use that information 30 min later, during a test phase. These results suggest that DA neurotransmission in the N.Acc. is crucial for foraging behavior when there is ambiguity about the location of reward in a spatial environment, but is not needed for efficient foraging behavior when an animal has previous information as to the location of rewarding stimuli. The results are discussed with respect to of the underlying physiological interactions between limbic glutamate and mesoaccumbens DA transmission in the N.Acc.