Impairment of LTP in insular cortex is correlated to resilience and vulnerability to chronic stress for PTSD

OBJECTIVE Exposure to stressful events can be differently perceived by individuals depending on the level of stress resilience or vulnerability.The neural processes that underlie such clinical y and social y important differences are largely unknown.As insula cortex is important in emotional processing,we have examined whether the changes in synaptic plasticity in the insula cortex involved in stress resilience or vulnerability.METHODS Mice were divided into two groups:control and stress group.Stress group was treated by foot electric shock twice daily(0.8 mA,2 s,ten times in 1 min) in continuous two weeks.Then we used fear conditioning test to detect re-experiencing of traumatic experience,open field test to detect avoidance,pre-pulse inhibition experiment to detect hyper arousal.The changes of synaptic plasticity in the insular cortex were recorded by the multiple channels electrophysiology and whole cell patch.RESULTS According to the behavioral scores,it was divided into resilient and vulnerable group.In the fear conditioning test,the vulnerable group showed the significant freezing time decreased than that of the resilient group(P<0.01).In the open field test,the time that enter the center zone of vulnerable group is increased than that resilient group(P<0.01);In the pre-pulse inhibition experiment,there are not significant difference of PPI value in both groups(P=0.4239).And then electrophysiological experiments are performed to detect the synaptic plasticity of the insular cortex.Compared with the resilient group,the LTP level was decreased(P<0.05) and the mEPSC was increased(P<0.01) in vulnerable group.CONCLUSION The impairment of synaptic plasticity in the insular cortex may be one of the neural mechanisms for the vulnerability to chronic stress.