Figure 6.

Extinction begun 1 or 3 h post-acquisition, but not immediately, is nifedipine-sensitive. (A) Experimental design (eight mice/group). Mice were subjected to cue fear acquisition followed by extinction in a different context either 0, 1, or 3 h later. Mice were injected with vehicle or nifedipine (40 mg/kg) 50 min prior to extinction. (B) Freezing 1 d after extinction during a 2-min acclimation period (Pre-CS) and two test CSs (white bars, vehicle treatment; black bars, nifedipine treatment). (^*) p < 0.05 vs. Vehicle; (+) p < 0.05 vs. Immediate-Vehicle.