Figure 1.

N/OFQ peptide impairs long-term recognition memory formation. A, Deficits in object discrimination induced by intracerebroventricular injections of N/OFQ (0.1, 0.3, and 1 nmol; n = 6–7 per dose). B, Deficits in object discrimination induced by bilateral N/OFQ infusions into the dorsal hippocampus (D. Hipp; 1 and 3 nmol/side; n = 7–9 per dose). In both experiments, N/OFQ was administered before the familiarization trial and memory performance was assessed drug-free 24 h later during the choice trial. Data are presented as mean discrimination index ± SEM. The dashed line materializes the chance level of 50% indicating equal exploration of both objects. C, Representative coronal section of the cannula placement in the dorsal hippocampus after cresyl violet acetate staining. The value indicates the distance in mm posterior to the bregma, according to the atlas of Paxinos and Watson (2001). **p < 0.01, significantly different from CSF-treated group.