D-amphetamine facilitation of Morris water task performance is blocked by eticlopride and correlated with increased dopamine synthesis in the prefrontal cortex

The effect of posttraining D-amphetamine on Morris water task (MWT) perform ance was analyzed in this study by training rats using a single training tr ial per day procedure. In addition to acquisition latency, learning was ass essed by a probe trial given 24 h after the last training trial. Rats given immediate post-trial D-amphetamine demonstrated improved performance over saline rats on both acquisition and the probe trial. An analysis of the mec hanisms underlying facilitation revealed that eticlopride (a D2 antagonist) blocked D-amphetamine's facilitatory effects on the probe trial and dopami ne synthesis was increased in the medial prefrontal cortex in the D-ampheta mine group relative to controls. These results show that chronic administra tion of posttraining D-amphetamine facilitated MWT performance, and this fa cilitation may be mediated by the dopaminergic system and dopamine synthesi s in the prefrontal cortex. (C) 2000 Elsevier Science B.V. All rights reser ved.