Figure 10. Acute stress causes delayed enhancement of contextual fear extinction retention.
Acute immobilization 2 days prior to contextual fear conditioning did not change percent time freezing during training (A), extinction (B) or 24-hr extinction probe (C) compared to control. Two-way ANOVA for extinction, effect of trial, p<0.0001. Acute immobilization 2 weeks prior to contextual fear conditioning did not change percent time freezing during training (D) or extinction (E) compared to control. Two-way ANOVA for extinction, effect of trial, p<0.0001. (F) Immobilized rats froze significantly less than controls in the 24-hr extinction probe. *p=0.04. (G) The number of surviving BrdU+ cells in the dorsal DG of immobilized rats did not differ from controls. (H) Immobilization does not alter the percent of BrdU+ cells co-expressing doublecortin (DCX) or glial fibrillary acidic protein (GFAP). (I) The percent of DCX+ immature neurons expressing cfos was greater in immobilized rats compared to controls. *p=0.02. All values are average ± SEM.