DIFFERENTIAL-EFFECTS OF LIDOCAINE INFUSIONS INTO THE VENTRAL CA1 SUBICULUM OR THE NUCLEUS-ACCUMBENS ON THE ACQUISITION AND RETENTION OF SPATIAL INFORMATION/

Reversible, lidocaine-induced lesions of the CA1/subicular subfield of the ventral hippocampus or the shell region of the nucleus accumbens (N.Acc.) were used to assess the roles of these structure during the a cquisition and retention of a spatial response as measured by the Morr is water-maze task. Acquisition and retention tests were administered over 2 phases of 6 trials, respectively. Rats receiving reversible les ions of the ventral CA1/subiculum prior to the acquisition phase of th is task required significantly longer path lengths to find a hidden pl atform than animals which received control infusions of artificial cer ebrospinal fluid. Rats with similar lesions to the N.Acc. were unimpai red. During the retention phase, 30 min after the acquisition phase, r ats with prior ventral CA1/subiculum or N.Acc. lesions had similar pat h lengths to control animals. Lidocaine infusions into either the vent ral CA1/subiculum or N.Acc. prior to the retention phase did not impai r performance relative to control animals. These results suggest that the N.Acc. is not involved in either the acquisition or retention of s patial information. In contrast, the ventral CA1/subiculum does appear to be involved in the initial use of novel spatial information necess ary for the performance of a spatially mediated escape response, but i s not involved in the retention or retrieval of previously acquired sp atial information.