Assessment Of Nucleus Accumbens Impairment In A Rat Model Of Postoperative Cognitive Dysfunction Using Diffusion Tensor Imaging

Objective:This study aims to investigate the diffusion tensor imaging（DTI）parameters of bilateral nucleus accumbens（NAc）at different time points in a postoperative cognitive dysfunction（POCD）model of depression,and their correlation with behavioral and histopathological changes.Methods:Twenty old male Sprague-Dawley（SD）rats were randomly divided into the POCD and Sham groups,with 10 rats in each group.The POCD group underwent exploratory laparotomy to establish a POCD depres-sion model,while the Sham group underwent a Sham operation.The FA and MD values of the bilateral NAc,behavioral changes of forced swimming test and sucrose preference rate,and pathological changes of glial fibrillary acidic protein（GFAP）fluorescent intensity were observed at 15 days(D₁₅)and 30days(D₃₀)after the operation.Results:The FA value of the bilateral NAc area in the POCD group was lower than that in the Sham group at the two time periods after the operation（P<0.05）.However,the MD value at D₃₀was higher in the POCD group than in the Sham group（P<0.05）.The FA value in the POCD group was lower at D₃₀than at D₁₅,and the MD value was higher at D₃₀than at D₁₅（P<0.05）.There were no significant differences in FA and MD values in the bilateral NAc area in Sham group（P>0.05）.Moreover,the floating time was prolonged while the sucrose preference rate was decreased in the POCD group compared with the sham group（P<0.05）.The floating time in the POCD group was longer at D₃₀than at D₁₅.However,the sucrose preference rate in the POCD was lower at D₃₀than at D₁₅.There were no significant differences in floating time and sucrose preference rate in Sham group（P>0.05）.The GFAP fluorescent intensity of the bilateral NAc region in the POCD group was significantly higher than in the Sham group（P<0.05）.Pearson correlation analysis showed that FA value was correlated with floating time and sucrose preference rate in the POCD group at D₁₅,while FA and MD value were correlated with floating time,sucrose preference rate and GFAP fluorescence intensity at D₃₀.Conclusions:Microstructural changes of the NAc area are associated with POCD related depression.FA and MD were demonstrated to be effective in monitoring postoperative depression and its severity.