Effect of preconditioning with nimodipine on postoperative cognitive dysfunction of aged rats

Objective To evaluate the effect of preconditioning with nimodipine on postoperative cognitive dys function of aged rats.Methods Ninety healthy male Sprague-Dawley rats,aged 18 months,weighing 400-500 g,were randomly divided into 3 groups (n =30 each) using a random number table:nimodipine control group (group N),surgery group (group S),and nimodipine + surgery group (N+ S group).In N and N + S groups,nimodipine 1 mg/kg was intraperitoneally injected,while the equal volume of normal saline was given instead in S group.30 min later,group N inhaled pure oxygen for 2 h,and S and N + S groups inhaled 1.8 ％ isoflourane for 2 h when splenectomy was performed.Morris water maze test was performed on 1 day before operation and 1st,3rd and 7th days after operation.After the end of Morris water maze test at 1 day before operation and 1st and 7th days after operation,10 rats were sacrificed and brains were removed and hippocampi were isolated for determination of apoptosis in hippocampal neurons,intracellular [Ca2+] i in cytoplasm,and hippocampal Bcl-2 and Bax mRNA expression and for examination of ultrastructure of hippocampal neurons.Results Compared with the value before administration,the escape latency was significantly prolonged,the frequency of crossing the original platform was decreased,apoptotic rate and [Ca2+]i were increased,Bcl-2 mRNA expression was down-regulated,and Bax mRNA expression and Bax/Bcl-2 mRNA ratio were up-regulated at each time point after operation in S and N + S groups,and no significant changes were found in the parameters mentioned above in N group.Compared with group S,the escape latency was significantly shortened,the frequency of crossing the original platform was inecreased,apoptotic rate and [Ca2+]i were decreased,Bcl-2 mRNA expression was up-regulated,and Bax mRNA expression was down-regulated at each time point after operation in group N + S.Pathological changes were found in S and N + S groups and the damage was severer in S group than in N + S group.Conclusion Nimodepine preconditioning can prevent postoperative cognitive dysfunction of aged rats,and inhibition of calcium overloadinduced apoptosis in hippocampal neurons may be involved in the mechanism. Key words: Nimodipine ;  Postoperative complications ;  Aged ;  Cognition disorders