The role of the hippocampal-nucleus accumbens pathway in radial-arm maze performance.

The role of the glutamatergic hippocampal-nucleus accumbens pathway in relaying hippocampal information via the nucleus accumbens to the motor system was investigated behaviorally using the radial-arm maze paradigm in rats. Bilateral injections of kynurenic acid, a glutamate antagonist, into the nucleus accumbens increased the latency to initiate movement during performance of an 8-arm radial maze with all arms baited and with 4 arms baited. Injections of kynurenic acid did not change the number of visits to previously visited arms (i.e. working memory errors) on both versions of the 8-arm radial maze. However, on the 8-arm radial maze with 4 arms baited, injections increased the number of visits to unbaited arms (i.e. reference memory errors). Similar injections were made in rats with ibotenic acid lesions of the prefrontal cortex in order to eliminate the glutamatergic prefrontal cortex-nucleus accumbens pathway so as to investigate the glutamatergic hippocampal-nucleus accumbens pathway. These rats displayed similar deficits on the radial-arm maze as non-lesioned rats (i.e. enhanced latency to initiate movement and reference memory errors). These findings suggest that the glutamatergic hippocampal-accumbens pathway plays a role in radial-arm maze performance by transferring information required for performing a radial-arm maze to the motor system.