DRL performance in 6-hydroxydopamine-treated rats.

Adult rats were given intraventricular injections of 6-hydroxydopamine (6-HDA) or saline-ascorbate vehicle prior to exposure to a differential-reinforcement-of-low-rate (DRL) 18-sec schedule of water reinforcement. The 6-HDA treatment did not alter the acquisition or maintenance of DRL performance despite large depletions of dopamine and norepinephrine in brain. The 6-HDA treatment completely blocked the response rate-increasing effects of amphetamine but did not alter the rate-decreasing effects of amphetamine on DRL performance. These findings suggest that 6-HDA-treated rats are able to responsd to the contingencies necessary to maintain reinforcement on a DRL schedule.