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-dependen tly increase the number of re-entries to arms (errors) during the rand om foraging task, in which 4 arms on an 8-arm maze are baited randomly . However, in a separate group of animals, similar infusions produce n o impairment when delivered prior to the test phase of the delayed spa tial win-shift task, which require the animal to acquire information d uring a training phase, and to use that information 30 min later, duri ng a test phase. These results suggest that DA neurotransmission in th e N.Acc. is crucial for foraging behavior when there is ambiguity abou t the location of reward in a spatial environment, but is not needed f or efficient foraging behavior when an animal has previous information as to the location of rewarding stimuli. The results are discussed wi th respect to of the underlying physiological interactions between lim bic glutamate and mesoaccumbens DA transmission in the N.Acc.