The effects of apomorphine on leverpress shock escape learning in rats

Four groups of rats (n = 10 each) were tested on a discrete trial leverpress shock escape task 15 min following an intraperitoneal injection of either 0 (saline), 0.5, 1.0, or 2.0 mg/kg apomorphine hydrochloride. The results indicated that all doses of apomorphine produced a severe disruption in escape performance. This disruption was temporary, however, as all apomorphine groups were responding as quickly as the saline control rats by the end of the training session. A comparison of the effects of apomorphine with the previously reported effects of scopolamine and septal lesions on shock escape learning revealed both similarities and differences. These findings suggest that a septal lesion-induced reduction of acetylcholine levels does not simply "unleash" an antagonistic dopaminergic system.