Sex comparison on long-lasting behavioral and physiological disturbances induced by single shock experience in rats

Enhanced female vulnerability and symptom severity are described in post-traumatic stress disorder (PTSD). It remains largely unknown whether females present with more pronounced PTSD-like symptoms than males in rodent models of PTSD. A model of single electric foot-shock followed by situational reminders was used to investigate in rats the impact of sex on potential long-lasting changes in anxiety-like behavior, and in endocrine and physiological responses to stress and fearful situations. Three weeks after single shock exposure (in the dark side of a shuttle box) both male and female rats spent less time in the dark compartment of a dark-light box and in the closed arms of an elevated plus maze than non-shocked controls. Both behaviors were likely due to avoidance of places reminiscent of the initial shock context. The shock exposure had no long-term impact on social interaction behavior or on basal and restraint stress-induced increases in plasma corticosterone. Shock exposure increased sudden silence-induced freezing responses and hyperthermia during novelty stress and fear to a similar extent in both males and females and left heart rate responses unaffected. Non-shocked females generally showed a reduced response or faster recovery to baseline under stress- or fearful test conditions as compared to non-shocked males, which was likely due to differential sex-specific coping strategies. Taken together, our results suggest that, despite some baseline sex differences, both male and female rats are similarly affected in the long-term by the initial foot-shock exposure used in this particular simulation of PTSD.