Figure 6.

Intra-mPFC injection of PEPA (0.02 μg) 30 min before extinction training facilitates extinction learning. A, Experimental design. Mice were trained for the contextual fear conditioning and tested 24 h (extinction training) and 72 h (extinction test) later. PEPA or vehicle (V) were microinjected into the mPFC or amygdala 30 min before extinction training. B, Location of the injection cannulas within the mPFC. Open circles, Vehicle; shaded circles, PEPA. C, Freezing time of mice microinjected with vehicle (n = 6) or PEPA (n = 5) into the mPFC in extinction training and test. *Statistically significant (p = 0.004 and 0.029 vs V in extinction training and test, respectively, two-tailed Student's t test). D, E, Changes in freezing time during the 360 s extinction training (D) and test (E) in groups injected with vehicle or PEPA. Data used in C were reanalyzed for the time course of changes in freezing time (bin = 60 s). *Statistically significant (p = 0.004, 0.017, 0.027, and 0.014 for bins 2–5, respectively, vs V in D, and p < 0.04 for all vs V in H, two-tailed Student's t test). F, Location of the injection cannulas within the amygdala. Open circles, vehicle; shaded circles, PEPA. G, Freezing time of mice microinjected with vehicle (n = 6) or PEPA (n = 5) into the amygdala in extinction training and test. The values in vehicle- and PEPA-injected groups are not significantly different in either extinction training or extinction test (p = 0.120 and 0.250 in extinction training and test, respectively, two-tailed Student's t test). Error bars indicate + SEM.