Electrolytic lesions of the ventral subiculum weakly alter spatial memory but potentiate amphetamine-induced locomotion

Abstract

Adult Long–Evans male rats were subjected to electrolytic lesions of the ventral subiculum, and tested for locomotor activity in the home cage, reference and working memory in the water maze, working memory in the radial maze, and d-amphetamine-induced locomotion (1 mg/kg, i.p.). When compared to their sham-operated counterparts, lesioned rats showed nocturnal hyperactivity, no reference memory deficit, but working memory was impaired in the water maze and during the initial stage of radial-maze testing. Their locomotor responsiveness to d-amphetamine was exagerated. Histological verifications confirmed lesions in the ventral subiculum. Material stained for acetylcholinesterase activity indicated septohippocampal and commissural/associational sprouting, accounting for partial damage to the perforant paths. These results showed that ventral subiculum lesions (i) do not alter the capability of rats to learn repeatedly presented spatial information, and (ii) impair, but do not prevent, spatial working memory, suggesting that the ventral subiculum is preferentially involved in short-term memory for spatial locations. Given the electrolytic nature of the lesion, the lesion-induced potentiation of the locomotor response to amphetamine is probably easier explained by partial disruption of the perforant paths than by damage to neurons of the ventral subiculum.