Figure 3
Effects of prelimbic (PL) cortex PKMζ inhibition by ZIP on the persistence of a reactivated contextual fear memory. (A) The general experimental design used. Animals were initially familiarized to Context A. A day later, the context was paired with three shocks (US). On the next day, 6 h after memory reactivation (Context A re-exposure), the animals received a bilateral infusion of ZIP or Scr-ZIP (10 nmol) intra-PL cortex. One, seven and 21 days later, the animals were re-exposed to pairing context (Tests A1, A2, and A3) to assess the ZIP effects on memory. (B) Effects of ZIP on memory persistence when given 6 h after reactivation. ZIP-treated animals presented less freezing time than controls during Tests A2 and A3, suggesting an impairment in memory persistence. (C) The general experimental design used. Animals were initially familiarized to Context A. A day later, the context was paired with three shocks (US). On the next day, 6 h after omitting memory reactivation (neutral and unpaired Context B exposure), the animals received a bilateral infusion of ZIP or Scr-ZIP intra-PL cortex. One, seven and 21 days later, the animals were re-exposed to the paired context (Tests A1, A2, and A3) to assess ZIP effects on memory. (D) ZIP effects on memory persistence when given 6 h after omitting memory reactivation. ZIP-treated animals presented freezing time similar to controls during any test, suggesting no changes in memory persistence. (E) The general experimental design used. Animals were initially familiarized to Context A. A day later, the context was paired with three shocks (US). On the next day, 6 h after memory reactivation (Context A re-exposure), the animals received a bilateral infusion of ZIP or Scr-ZIP intra-PL cortex. Ten days later, the animals were re-exposed to the paired context (Test A1) to assess ZIP effects on memory. (F) Effects of ZIP on memory persistence when given 6 h after reactivation. ZIP-treated animals presented less freezing time than controls during Test A1, suggesting an impairment in memory persistence. Values are expressed as mean ± S.E.M (number of animals per group: B = 7/group; D = 6–9; F = 7–9). In “B” and “F”, the asterisk denotes a statistically significant difference (P < 0.05) from the respective control group (mixed ANOVA followed by the Tukey test). In “D”, the fence (hashtag) denotes a statistically significant difference (P < 0.05) from Tests A1, A2 and A3 relative to the no reactivation session in both groups (mixed ANOVA followed by the Tukey test).
