Figure 9.

Central administration of NPY enhances the extinction of fear-potentiated startle. A, Animals were implanted with intracerebroventricular cannulae 7–10 d before behavioral testing. Animals were baseline tested, trained, and matched with a preextinction test (Pre-Ext) in our standard context. The context was altered for extinction training and testing to decrease the possible confounding effects of contextual conditioning. Before extinction training (30 min), animals were infused with either vehicle or 10 μg of NPY. Animals were tested for extinction retention (Post-Ext) 48 h later off drug. B, Animals infused with NPY had significantly lower percentage fear-potentiated startle during the Post-Ext test than vehicle controls. Additionally, the NPY group shows a significant reduction in percentage fear-potentiated startle from Pre-Ext to Post-Ext, while there is no significant change in the vehicle group. (error bars indicate ±SEM; **p < 0.05 compared with vehicle Post-Ext, p < 0.001 compared with NPY Pre-Ext). C, There was no difference in overall startle amplitude or baseline startle between groups.