Study On The Cerebrovascular Reserve Capacity For Rats Under Chronic High Altitude Hypoxia Using CTP Combined With Methazolamide Stress Test

Objective: To explore the changes of cerebrovascular reserve and the compensatory process of cerebrovascular reserve in SD rats exposed to chronic high altitude hypoxia for 30 weeks using CT perfusion scan and acetazolamide stress experiment.Methods: Twenty healthy 4-week-old SD rats were randomly divided into plateau group(n = 10)and plain group(n = 10).The rats in plateau group were transported to Yushu area of Qinghai province(average altitude about4200m)for 30 weeks,and those in plain group were transported to Che ngdu area in Sichuan province(average altitude about 500m)for 30 weeks.After 30 weeks of feeding,CT perfusion scan and acetazolamide load test were performed in plateau group and plain group,and further blood and pathological samples were collected.After collecting the relevant data,statistical processing was carried out.Results:(1)In the resting state or excited state,there were significant differences in CBF,CBV,TT and TT values between the plateau group and the plain group rats in the cerebral cortex(Cx)(P<0.001).The difference of Cx CVR between high altitude group and plain group rats was statistically significant(P<0.001).There were significant differences in CBF,CBV,MTT and TTP of Cx between resting state and excited state in high altitude group rats((P<0.001),and the parameters of Cx in excited state were significantly higher than those in resting state in high altitude group rats,while there were significant differences in CBF,CBV and TTP of Cx between resting state and excited state in plain group rats(P<0.001),but there was no significant difference in MTT value(P>0.05).(2)There were significant differences in MVD,HIF-1 α and VEGF-A of Cx between high altitude group and plain group rats(P<0.001).No abnormality of HE staining was found in plateau group and plain group rats.(3)In the correlation analysis,CBF was negatively correlated with HCT and MVD,while TTP was positively correlated with HCT and MVD.Conclusion: The cerebrovascular reserve capacity of rats exposed to chronic high altitude hypoxia for 30 weeks is lower than that of plain rats,suggesting that the cerebrovascular reserve capacity is impaired.The CBF and CBV values of rats exposed to chronic high altitude hypoxia for 30 weeks decreased and showed a state of cerebral hypo-perfusion.