EFFECTS OF LESIONS OF THE SUBSTANTIA INNOMINATA VENTRA PALLIDUM, GLOBUS-PALLIDUS AND MEDIAL SEPTUM ON RATS PERFORMANCE IN OBJECT-RECOGNITION AND RADIAL-MAZE TASKS - PHYSOSTIGMINE AND AMPHETAMINE TREATMENTS

The present study examined the effects of electrolytic lesions of the Medial Septum/Vertical Diagonal Band of Broca (MS/VDBB), the Globus Pa llidus (GP) and the Substantia-Innominata/Ventral Pallidum (SI/VP) on the performance of rats in object-recognition memory and radial-maze l earning tests. In the latter test, subgroups of sham-operated, MS/VDBB , SI/VP and GP rats were treated with saline, amphetamine or physostig mine. (1) In the object recognition task, the level of discrimination was significantly lower in GP compared to SI/VP and in both GP and SI/ VP compared to Control and MS/VDBB groups, however, only GP did not di scriminate between new and familiar objects; (2) in the radial-maze ta sk, GP and SI/VP lesions produced weak and transient impairment wherea s MS/VDBB lesions produced a large deficit; (3) in the radial-maze tas k, performance of normal rats was improved with physostigmine and impa ired with amphetamine. The effect of amphetamine was significant on no n-memory measures only; (4) neither amphetamine nor physostigmine impr oved memory performances of lesioned rats. These results suggest that the septo-hippocampal projections are involved in spatial memory but n ot in object recognition whereas the integrity of Substantia Innominat a/Ventral Pallidum does not seem critical for either task. The choline rgic nature of the deficit produced by the medial septal lesion remain s in question because of improvements seen in sham-operated rats but n ot in lesioned rats. (C) 1998 The Italian Pharmacological Society.