Figure 3.

Effects of priRet followed by the RE procedure on remote fear memory. (A) Schema of the experimental protocol. Animals were trained for contextual fear conditioning and then were divided into four groups. The RE procedure was performed 36 days after fear training, and priRet was presented 0 min (n = 11), 1 h (n = 7), 24 h (n = 7), or 35 D (n = 9) before the RE procedure. One day after RE, T1, RS, and T2 were performed 24 h apart. (B) All rats acquired comparable conditioned contextual fear as they received three footshocks. (C) Fear levels during priRet were similar among groups. (D) There were no significant group differences of freezing during retrieval and extinction sessions. All rats showed significant fear attenuation within extinction sessions. (E) The extinguished fear of rats in the 0 min, 1 h, and 24 h groups did not exhibit any return, but the 35 D group showed significant reinstatement. The data are expressed as mean ± SEM. n.s., not significant, ^**P < 0.01.