Figure 1. Experimental design.

CS-US denotes pairings of a tone with footshock, while CS denotes presentations of the tone alone. In Experiment 1 norBNI (10 µg or 5 µg) or saline was infused into the ventral hippocampus. In Experiment 2 norBNI (10 µg) or saline was infused into the dorsal hippocampus. Animals were tested for responses to the tone in both contexts in a counterbalanced order. norBNI was infused 24 hours prior to the beginning of test due to the slow onset latency of the drug.