QUINPIROLE AND D-AMPHETAMINE ADMINISTRATION POSTTRAINING ENHANCES MEMORY ON SPATIAL AND CUED DISCRIMINATIONS IN A WATER MAZE

Two behavioral testing procedures, a spatial discrimination and a cued discrimination, were used in a water maze to assess memory enhancemen t following posttraining administration of d-amphetamine, an indirect catecholamine agonist, and quinpirole, a dopaminergic D2 receptor agon ist. Rats received an eight-trial (30-sec intertrial interval) trainin g session on a single-platform spatial or cued discrimination in a wat er maze. In the spatial task, a submerged escape platform was located in the same quadrant of the maze on all trials. In the cued task, a vi sible escape platform was located in a different quadrant of the maze on each trial. Following Trial 8 in both tasks, the rats received a po sttraining subcutaneous injection of d-amphetamine (1.0 mg/kg), quinpi role (LY 171555; 2.0 mg/kg), or saline. On a retention test session 24 h later, latency to mount the escape platform was used as a measure o f memory. In both tasks, the retention test escape latencies of the an imals given d-amphetamine or quinpirole were lower than those of the s aline-injected controls. In both tasks, injections of d-amphetamine an d quinpirole did not affect retention when administered 2 h posttraini ng, indicating a time-dependent effect of the posttraining treatments on retention. Control experiments indicated that the effects of cl-amp hetamine on retention were not due to enhancement of memory of a ''sea rch strategy'' common to both tasks. Rather, the effects of the drug o n retention were due to an influence on memory for the ''type'' of dis crimination learned (i.e., spatial or cued). The findings indicate tha t both spatial and cued discriminations in a water maze are sensitive to posttraining memory enhancement, and they suggest a neuromodulatory role for dopaminergic systems in both tasks.