Effect Of Controlled Hypotension On Expression Of Microglias And HSP70 In Brain Hippocampus CA1 Subregion In The Rats

Objective: Controlled hypotension has been generally used inanaesthetic practice. It is generally accepted that controlled hypotensionis safe when mean arterial pressure(MAP) is large than 50mmHg innormotension patients. When MAP is low to 50mmHg, hypotension mayresult in ischemia and hypoxia of tissue; reduction of blood pressurebelow the autoregulatory limits of cerebral blood flow(CBF) may impairsCBF and consequently jeopardizes brain tissue intergrity and leading toischemic injury. Many studies have different argument on effect ofhypotenson on cerebral tissue, and it is not very clear today. Our studyproduce hypotension induced by sodium nitroprusside(SNP) andesmolol(ESM) in the rats, to explore change of survival rate, neurologicand behavioral assessment and brain tissue morphological after differentextent lasting hypotension, and to understand tolerance of hypotensionand effect of hypotension on brain.Methods: 56 SD rats were randomly divided into 4 groups: Agroup(control), B group(level of MAP70mmHg), C group(level of MAP50mmHg), D group(level of MAP30mmHg); the combination ofsodium nitroprusside(SNP) and esmolol induce hypotension and retain 1hhypotension; each group set two time point after controlled hypotension:1 day and 7 day; So eight groups: A1, A7, B1, B7, C1, C7, D1, D7, eachgroup contain 7 SD rats. recording vital sign of rats and doing blood gasanalysis during controlled hypotension, and observing survival rate,neurologic and behavioral assessment and brain tissue morphologicalchange after hypotension.Result:1. One day after hypotension, survival rate in four group were all 100%,seven day after hypotension, survival rate in group A, B, C and Dwere respectively: 100%, 100%, 100%, 86%. there were littledifference(P＞0.05).2. No pathology sign were observed in 1 and 7 day after hypotension infour group. Neurologic and behavioral assessment in four group hadlittle difference(P＞0.05).3. HE staining: there were no significant changes of cell apoptosis anddeath in group A, B, C and D. there are normal cells mainly.4. Microglias in rat hippocampus: the hippocampus were significantlystained in group D1, slightly stained in all other groups; averageoptical density in group D1 were significantly higher than in othergroups(P＜0.05). 5. HSP70 immunohistochemical staining: there were negative expressionof hsp70 in all eight group(P＞0.05).Conclusions:1. There were no pathology sign and abnormal neuroethology after 1hhypotension of MAP 30mmHg induced by SNP and ESM, and no cellapoptosis and death in brain hippocampus section.2. Activated microglias happen in brain hippocampus after 1hhypotension of MAP 30mmHg induced by SNP and ESM, but rats cantolerate this hypotension. More study are requested to confirm whatdegree MAP can result in brain injury obviously.3. HSP70 do not express in brian hippocampus after 1h hypotension ofMAP 30mmHg induced by SNP and ESM.