Data for Post-training corticosterone treatment differentially modulates recent and remote contextual fear specificity

Overgeneralized fear has long been implicated in generalized anxiety (GAD) and post-traumatic stress disorder (PTSD), however, mechanisms underlying memory consolidation are still not completely understood. Previous studies have revealed that stronger fear conditioning training protocols are associated with both increased post-training corticosterone (CORT) levels and fear responses at retrieval tests. Additionally, exogenous CORT administered immediately post-training modulates memory consolidation following an inverted U-curve trendline. Here we used discriminative contextual fear conditioning (CFC) to investigate the role CORT plays in the consolidation of fear memories, focusing in memory specificity. Adult male Wistar rats were exposed to CFC training with two footshock intensities (0.3 or 0.6mA, in separate groups of animals) and were immediately treated with CORT-HBC complex (4.0mg/kg or 8.0mg/kg. Sigma-Aldrich C174) or saline (2mL/kg). Two days later, rats were tested for memory specificity first in a novel context (B) and 1 min after, in the training context (A). Order (B-A) was validated by a previous pilot experiment done in our lab. Freezing time (s) was used to measure memory strength and an Index of Generalization (IG) was calculated using the formula [ (s) B / ( (s) A + (s) B)]. The range expected for IG is from 0 (optimal discrimination) to 0.6 (optimal generalization). IG Values around 0.3 are intermediate between generalization and discrimination. The procedures and experimental design was approved by CEUA-UFABC under process #5553080618.