| Objective:To summarize the changes of functional magnetic resonance imaging(f MRI)parameters in the bilateral hippocampal CA1 region of the hemorrhagic shock reperfusion(HSR)model of rats and their correlation with histopathological results and behavioral tests,and to explore the f MRI indicators for evaluating the hippocampal injury of HSR and its effect on long-term cognitive function.Methods: Rats were randomly divided into HSR group and Sham group for two phase study.At the early stage,24 rats in each group were subdivided into 4 time points(3 h,6 h,12 h and 24 h)for MRI and histopathological examination.In the long term,30 rats in each group were subdivided into 5 periods(1 w,2 w,4 w,8 w and 12 w)for MRI,behavioral and histopathological examination.1.f MRI:(1)Cerebral blood flow(CBF)in bilateral hippocampus CA1 area was detected using 3D-arterial spin labeling(3D-ASL).(2)Fractional anisotropy(FA),mean diffusivity(MD),axial diffusivity(Da),radial diffusivity(Dr),mean kurtosis(MK),axial kurtosis(Ka)and radial kurtosis(Kr)in bilateral hippocampal CA1 area was measured using Diffusion kurtosis imaging(DKI).The differences of f MRI parameters were compared between and within the two groups.2.Histopathology was used to detect the early apoptosis rate,pyroptosis rate and long-term the fluorescence intensity of glial fibrillary acidic protein(GFAP)in bilateral hippocampal CA1.3.Behavioral changes: The Morris water maze experiment was used to detect the escape latency,distance and time spend in the target quadrant.The distance,speed and rearing/leaning were measured by open field experiment.4.Pearson correlation analysis was used to test the correlation between the f MRI parameters and the rate of pyroptosis and apoptosis,as well as behavioral indicators and the fluorescence intensity of GFAP in rats.Results: 1.Comparision of f MRI parameters in bilateral hippocampal CA1 region of the two groups in the early stage: CBF in HSR group was significantly lower than that in Sham group,MK,Ka and Kr in HSR group were all higher than those in Sham group,FA at 12 h and 24 h in HSR group were lower than those in Sham group,MD,Da and Dr at 3 h and 6 h in HSR group were lower than those in Sham group,while MD and Da at 24 h in HSR group were significantly higher than those in Sham group.All the differences were statistically significant(P<0.05).2.The apoptosis rate and pyroptosis rate in HSR group were significantly higher than that in Sham group in early term(P<0.05).3.The comparision of f MRI parameters in bilateral hippocampal CA1 region between the two groups in the long-term stage: The values of MK,Ka and Kr in HSR group were higher than those in Sham group at each time point.The FA value of 1 w in HSR group was lower than that in Sham group.The MD value of 1 w in HSR group was higher than that in Sham group.The differences were statistically significant(P<0.05).4.The results of Morris water maze experiment in long-term : The escape latency in HSR group at the 1st day of 4w,8w and 12 w and at the 2nd to 4th day in each period was significantly longer than that in the Sham group(P<0.05).The distance and time spend in target quadrant in HSR group were significantly shorter than those in Sham group(P<0.05).In the open-field experiment,compared with Sham group,HSR group had shorter moving distance,slower speed and fewer rearing/leaning times(P<0.05).5.The fluorescence intensity of GFAP in the bilateral hippocampal CA1 region in the HSR group was higher than that in the Sham group(P<0.05).6.Pearson correlation analysis showed that CBF,FA,MK,Ka and Kr values in early-stage were strongly correlated with apoptosis rate and pyroptosis rate,MK,Ka and Kr were strongly correlated with the fluorescence intensity of GFAP(P<0.05).Conclusions: 1.In the early stage,CBF,FA,MK,Ka and Kr values can accurately evaluate the abnormal blood perfusion and microstructure changes in hippocampal CA1 area of the incomplete cerebral ischemia reperfusion rats induced by HSR,and can reflect the increasing trend of the apoptosis rate and pyroptosis rate.2.In the long-term stage,MK,Ka and Kr values were sensitive to the injury in hippocampal CA1 region of HSR rats,which could reflect astrocyte proliferation,but f MRI parameters could not reflect the change of behavioral disorders sensitively. |
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