Effects of scopolamine and l-NAME on rats' performance in the object location test

The object location task is a new procedure evaluating spatial memory abilities in the rat. The aim of the present study was to characterize this behavioural paradigm by pharmacologic means. For this purpose, the effects of the muscarinic receptor antagonist scopolamine and the inhibitor of the nitric oxide synthase l-NAME on object location were assessed in the rat. In a first study, object location was impaired when the delay condition of 60-min was utilized. Subsequently, pre-training administration of scopolamine (0.2 mg/kg but not 0.07 mg/kg) induced delay-dependent performance deficits in this test. These impairments seem to be centrally mediated since the peripheral muscarinic receptor antagonist methylscopolamine (0.2 mg/kg) did not affect object location under the same conditions. Finally, pre-training treatment with l-NAME (30 mg/kg but not 10 mg/kg) also induced delay-dependent performance deficits in the object location task. These results indicate that the object location test is sensitive to pharmacological treatment and could be used for assessing the therapeutic potential of promnesic compounds.