Abstract
The effects of amphetamine along the rostrocaudal axis of the nucleus accumbens (NAcc) on ventral tegmental area (VTA) intracranial self-stimulation (ICSS) were studied. Eighteen rats were trained to lever press for ICSS in the VTA. Rate-frequency functions were determined by logarithmically decreasing the frequency of cathodal pulses in a stimulation train from a value that induced maximal responding to one that induced no responding (thresholds). After ICSS thresholds stabilized, (+)-amphetamine (20.0 μg/0.5 μl) or its vehicle, distilled H 2O (0.5 μl), were injected directly into the rostral NAcc ( n = 6) or the caudal NAcc ( n = 8) or the caudate-putamen (CP) ( n = 5) just dorsal to the caudal NAcc. Results showed that amphetamine in the caudal NAcc significantly decreased ICSS thresholds without affecting asymptotic rates of responding, indicating a potentiation of the rewarding efficacy of VTA stimulation. Amphetamine in the rostral NAcc or CP produced smaller, non-significant, decreases in ICSS thresholds. Further analyses revealed a significant positive correlation ( r 13 = 0.51, P < 0.05) between the site of injection along the rostrocaudal axis of the NAcc and the size of the amphetamine-produced potentiation of VTA stimulation reward. Others have reported topographical differences, including dopamine terminal density and D 1 receptor density, in the NAcc. The present results indicate that these anatomical and neurochemical differences appear to be correlated with behavioural differences.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call