Development and treatment of cognitive inflexibility in sub-chronic stress-re-stress (SRS) model of PTSD.

BACKGROUND

Cognitive inflexibility is one of the major clinical symptoms of post-traumatic stress disorder (PTSD). Studies have examined the impact of traumatic events on anxiety. However, there were limited reports on the effect of traumatic episodes on cognitive flexibility. Therefore, animal models developing cognitive inflexibility would provide new insight of pathophysiology and pharmacotherapy of PTSD.

METHODS

Male Wistar rats were subjected to stress-re-stress (SRS) procedure by restraining them for 2 h followed by foot shock (FS) and halothane exposure on day 2 (D-2). Then, the rats were exposed every week to FS as re-stress cue up to D-32. Donepezil (3 mg/kg; po) and sertraline (10 mg/kg; po) dosing was started from D-8 and continued up to D-32.

RESULTS

SRS exposure caused cognitive inflexibility by producing deficits in intra-dimension (ID) and extra-dimension (ED) set-shifting which was significantly attenuated by donepezil. However, sertraline mitigated only ID shift in SRS-subjected rats. SRS-induced PTSD-like symptoms such as fear response, anxiety-like behaviour and cognitive deficits were attenuated by both donepezil and sertraline. Donepezil did not modulate the SRS-induced hypothalamic-pituitary-adrenal (HPA) axis dysfunction and activation of serotonergic and nor-adrenergic system. Interestingly, exposure of SRS caused a decrease in acetylcholine level and increase in acetylcholine esterase activity in prefrontal cortex (PFC) and hippocampus (HIP) which was only mitigated by donepezil. Donepezil significantly attenuated SRS-induced down-regulation of choline-acetyl transferase and α-7 nicotinic acetylcholine receptor expressions in PFC and HIP.

CONCLUSION

Cognitive inflexibility is developed in the SRS model along with other PTSD-like symptoms which were attenuated by donepezil.