Long-term effects of traumatic stress on subsequent contextual fear conditioning in rats

Abstract

Exposure to stressful events affects subsequent sensitivity to fear. We investigated the long-term effects of a traumatic experience on subsequent contextual fear conditioning and anxiety-like behaviors in rats (Experiment 1). In addition, we tested whether the administration of the glucocorticoid synthesis inhibitor metyrapone (MET) attenuated the sensitization of fear induced by traumatic stress (Experiment 2). Male rats were subjected to a multiple stress (MS) session, which consisted of 4 foot shocks (1mA, 1s) and forced swimming for 20min, followed by exposure to a situational reminder 7days after the MS session. MET (25 or 100mg/kg, intraperitoneal) was administered 30min before MS. The contextual fear conditioning was performed 14days after MS. MS enhanced the conditioned fear response for at least 14days after the conditioning, and pretreatment with MET did not affect the enhancement of conditioned fear. These results suggest that glucocorticoid secretion triggered by MS is not involved in regulating the long-term stress-induced sensitization of fear.

Keywords: Contextual fear conditioning; Contextual reminder; Corticosterone; Metyrapone; Open field behavior; Post-traumatic stress disorder; Rat.