EFFECTS OF LESIONS OF THE SUBSTANTIA INNOMINATA r VENTRAL PALLIDUM, GLOBUS PALLIDUS AND MEDIAL SEPTUM ON RAT’S PERFORMANCE IN OBJECT-RECOGNITION AND RADIAL-MAZE TASKS: PHYSOSTIGMINE AND AMPHETAMINE TREATMENTS

The present study examined the effects of electrolytic lesions of the Medial SeptumrVertiŽ . Ž . cal Diagonal Band of Broca MSrVDBB , the Globus Pallidus GP and the SubstantiaŽ . InnominatarVentral Pallidum SIrVP on the performance of rats in object-recognition memory and radial-maze learning tests. In the latter test, subgroups of sham-operated, MSrVDBB, SIrVP and GP rats were treated with saline, amphetamine or physostigmine. Ž . 1 In the object recognition task, the level of discrimination was significantly lower in GP compared to SIrVP and in both GP and SIrVP compared to Control and MSrVDBB Ž . groups, however, only GP did not discriminate between new and familiar objects; 2 in the radial-maze task, GP and SIrVP lesions produced weak and transient impairment whereas Ž . MSrVDBB lesions produced a large deficit; 3 in the radial-maze task, performance of normal rats was improved with physostigmine and impaired with amphetamine. The effect Ž . of amphetamine was significant on non-memory measures only; 4 neither amphetamine nor physostigmine improved memory performances of lesioned rats. These results suggest that the septo]hippocampal projections are involved in spatial memory but not in object recognition whereas the integrity of Substantia InnominatarVentral Pallidum does not seem critical for either task. The cholinergic nature of the deficit produced by the medial septal lesion remains in question because of improvements seen in sham-operated rats but not in lesioned rats. Q 1998 The Italian Pharmacological Society