Figure 1.

Freezing behaviors of VPAC2-KO mice in the fear conditioning test. On Day 1, mice were trained with 5 tone-shock pairings (A). Then, mice were subjected to the contextual fear memory test on Day 2 (B), cued fear memory test on Day 3 (C), and cued fear extinction paradigm on Days 4 and 5 (D). Results are expressed as the mean ± S.E.M. of 14 mice per group. BL: Baseline. ^††P < 0.01, compared with the baseline. *P < 0.05, **P < 0.01, compared with wild-type.