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 t he nucleus accumbens were studied across the anteroposterior axis of this n ucleus. 2. Amphetamine (0.05; 0.10; 0.50; 1.00 mu M) produced a dose-dependent incr ease in locomotor activity after microinfusion into either the rostral shel l, 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 cor e. 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 ros tral shell. In contrast, the highest dose of amphetamine significantly incr eased dialysate serotonin levels over baseline only in the caudal shell of the nucleus accumbens. 4. These results demonstrate the preferential effect of amphetamine on dopa mine in the rostral shell and serotonin in the caudal shell subterritory of the nucleus accumbens.