Differential effects of immediate posttraining sulpiride microinfusions into the nucleus accumbens shell and core on Morris water maze retention

Extensive evidence indicates that the nucleus accumbens is involved in spat ial learning and memory tasks. There has been relatively little inquiry, ho wever, into which of the two anatomically and functionally distinct subregi ons of the nucleus accumbens (the shell and the core) mediate this involvem ent. To investigate this issue, male Sprague-Dawley rats implanted with bil ateral intracerebral guide cannulae aimed at the medial shell or core were given eight training trials in the standard hidden platform version of the Morris water maze, immediately followed by intracerebral microinfusions of the D2 dopamine antagonist sulpiride or saline vehicle. A probe trial reten tion test 2 days later revealed that sulpiride microinfusions into the shel l significantly increased latency to reach the platform location, whereas s ulpiride microinfusions into the core significantly decreased the time spen t swimming near the platform location and significantly increased the time spent swimming in the maze periphery. The results suggest that the nucleus accumbens shell and core may be involved in the consolidation of memory for different aspects of water maze task performance.