Figure 5.

Effects of post-priRet LVGCC blockade on recent fear memories. (A) Schema of the experimental protocol. Animals were trained for contextual fear conditioning on day 1. They were then divided into three groups. PriRet was performed after fear training on day 2. NIMO (0 h NIMO, n = 8) or vehicle (VEH, n = 9) was systemically injected immediately after priRet. Another group of rats were injected with NIMO 6 h after priRet (6 h NIMO, n = 8). On day 3, the RE procedure was conducted. T1, RS, and T2 were then performed 24 h apart as in previous experiments. (B) All rats acquired comparable conditioned contextual fear as they received three footshocks. (C) Fear levels during priRet were similar among groups. (D) All rats showed significant fear attenuation within extinction sessions and there were no significant group differences of freezing during retrieval and extinction sessions. (E) Rats in the 0 h NIMO groups exhibited no significant fear return, suggesting the systemic injection of NIMO immediately after priRet recovered the fear-disrupting effect of the subsequent RE procedure. This fear-disrupting effect of the RE procedure was not regained when vehicle was injected or NIMO was administrated 6 h after priRet. The data are expressed as mean ± SEM. n.s., not significant, ^**P < 0.01.