Behavioral neurochemistry reveals a new functional dichotomy in the shell subregion of the nucleus accumbens

1. The behavioral and neurochemical effects produced by the direct infusion of amphetamine by reverse microdialysis into either the core or shell of the nucleus accumbens were studied across the anteroposterior axis of this nucleus. 2. Amphetamine (0.05; 0.10; 0.50; 1.00 mu M) produced a dose-dependent increase in locomotor activity after microinfusion into either the rostral shell, caudal shell or core of the nucleus accumbens. However, the amphetamine-induced locomotor activating effect was significantly higher in the rostral shell of the nucleus accumbens compared with both the caudal shell and core. 3. The lowest concentrations of amphetamine produced an equipotent decrease in dialysate dopamine in either the rostral shell, caudal shell, or core. At 1.0 mu M, however, amphetamine selectively increased dopamine in the rostral shell. In contrast, the highest dose of amphetamine significantly increased dialysate serotonin levels over baseline only in the caudal shell of the nucleus accumbens. 4. These results demonstrate the preferential effect of amphetamine on dopamine in the rostral shell and serotonin in the caudal shell subterritory of the nucleus accumbens.