Changes of postoperative cognitive function after incomplete cerebral ischemia in rats and its pathological mechanism

Objective To investigate the changes of cognitive function and the apoptosis of hippocampus neuron in CA1 of rats after incomplete cerebral ischemia. Methods Thirty healthy and clean male SD rats were randomly assigned into 2 groups: sham operation group(SO group,n=15) and incomplete cerebral ischemia model group(IS group,n=15).The model of incomplete cerebral ischemia was built by bilateral carotid artery occlusion technique.The rats in SO group were only dissected to expose the blood vessels but not clip.Morris water maze equipment was used to inspect the cognitive function after ischemia for 2,3,4,5 d and 7 d respectively.Seventy-two healthy and clean male SD rats were randomly assigned into 2 groups: sham operation group(SO group,n=36) and and incomplete cerebral ischemia model group(IS group,n=36).According to the different cerebral ischemia time,all rats were assigned into 6 groups(6 in each group).The rats were executed,the hippocampus was extracted after ischemia for 24 h,48 h,72 h,4 d,5 d and 7 d to analyze the apoptosis rate by flow cytometry. Results Compared with SO group,the latency in IS group was prolonged at 1 d and 4 d after training,but there was no significant difference(P0.05).At 2 d and 3 d after training,the latencies in IS group were prolonged significantly compared with SO group(P0.05).Compared with SO group,the frequency of passing the virtual platform and the time of staying in virtual platform in IS group were less than in SO group(P 0.05).The flow cytometry showed that the hippocampal neuron apoptosis rate showed no significant change in SO group at different time points,while the apoptosis rate in IS group began to increase at 24 h,and peaked at 72 h,then decreased gradually.The hippocampal neuron apoptosis rates were significantly higher in IS group than in SO group at different time points(P0.05),especially at 3 d(P0.01). Conclusion After incomplete cerebral ischemia,the decrease of cognitive function may be related with the increase of hippocampal neuron apoptosis.