Effects Of Sevoflurane Precondition On Cognitive Function In Rats Of Acute Myocardia Reperfusion Injury And Its Mechanism

Cardial ischemia reperfusion injury(IRI)is still hardly avoided when the following conditions happened such as thrombolysis,unstable angina,open heart operation,heart lung transplantation and cardiopulmonary resuscitation.The prevention of organ IRI is also an important question to be solved urgently.Sevoflurane can reduce myocardial oxygen consumption by dilating coronary artery,reducing myocardial contractility,and reduce Ca²⁺inflow directly,active K_ATPchannel to lessen myocardial reperfusion injury; it also can influence the function of mitochondrion in CNS by changing membrane potential,active signal channel of mitochondrion to protect the brain.Acute myocardial reperfusion injury inhibits LTP and induces the elevation of inflammatory cytokine in the hippocampus.LTP is a classical index to study the plasticity of the nerve synapse related to learning memory.It has been reported that the elevation of inflammatory cytokine in CNS plays roles in the impairment of the space learning ability.The aim of our study is to observe the effects of sevoflurane precondition on LTP and expression of TNF-αmRNA,IL-1βmRNA in hippocampus in rats of acute myocardial reperfusion injury.Materials1.experimental animal:60 healthy Wistar rats,30 male and 30 female,weight ranges from 300g to 500g, supplied by experimental animal center of China Medical University.2.Chemical and reagents:pentobarbital sodium(ShangHai);sevoflurane(Abbott,American);polyclonal antibody(Santa,USA);Trypsin(1:250)(Amresco,USA);DMEM(Gibco, USA);Trizol(Invitrogen,USA);RT-PCR kit(Promega,USA);PVDF(Bio-Rad, USA);CK and LDH kit(zhongshan,Beijing).3.Experiment instruments:Ohmeda 7000 Anesthesia machine(Ohmeda,U.S.A),Animal ventilator(Havard 638,U.S.A),inverted phase contrast microscope(OLYMPUS,Japan);desk centrifuge (SIGMA 1-13,USA);PTC-100PCRamplificator(USA);electrophoresis image analysator(Alphainnotech Chemilmager 5500,U.S.A);CO₂ incubator(KENDRO/ HERAEUS,German);super clean bench(Suzhou,China);PowerPac200 electrophoretic apparatus(BIO-RAD,USA);MDF-U ultra deep-freeze equipment(SANYO,Japan); micro image analysis system(Olympus AX70/Coolsnapfx/MetaMorph,Japan).Methods1.The effects of sevoflurane precondition on LTP:set up rats model of acute myocardial reperfusion injury.Collect blood from femoral vein,measure CK and LDH concentration on the time of just before occluding LVA(T₁),30min after occluding (T₂)and 120min after reperfusion(T₃).Totally 60 rats were randomly divided into 4 groups:group A(n=6),B(n=18),C(n=18)and D(n=18).In group B,Left ventricular artery(LVA)was exposed but not occluded.In group C LVA was occluded by thread (5-0)for 30min then loose it for 120min.In group D,rats inhaled 1.0MAC sevoflurane 60mins before LVA was occluded.LTP was measured at different time point to observe space learning abilities on the 1^st,3^rd,7^thday after surgery,respectively, which was divided into B1,B3,B7 subgroup,C1,C3,C7 subgroup and D1,D3,D7 subgroup,6 rats for each subgroup.2.The effects of sevoflurane precondition on brain protection:The expressions of TNF-αmRNA and IL-1βmRNA in hippocampus were studied by RT-RCR and the proteins were measured by western blot.ResultsLTP were inhibited significantly in C1,D1 and C3,D3 group than in group A; The degree of inhibition was lower in D1,3group than in C1,3group(P＜0.05).As compared with group A,TNF-αmRNA expression in hippocampus was significantly higher than that in C1,D1 group;TNF-αmRNA expression was lower in D1 group than in C1 group(P＜0.05).There was no significant difference in the expression of TNF-αamong all the groups(P＞0.05).IL-1βmRNA expression was higher in the C1,D1 and C3,D3group than those in the other groups.The IL-1βwas higher in group C1 than that in the A,B1,D1group(P＜0.05).DiscussionOccluding the anterior descending branch of LVA is a classical method to set up acute myocardial reperfusion injury model.ECG showed ST-T elevated inâ… lead after tightening the thread,and depressed above 1/2 after loosing,which can prove myocardial ischemia.Snip the thread after ischemia 30min,the myocardial color changes significantly and reperfusion arrhythmia appear,which proves the recovery of myocardial perfusion.In our study,the elevation of ST-T section and increase of LDH and CK suggested the success of setting up acute myocardial reperfusion injury model. Space learning ability reflects the physiological function.In CNS,hippocampus is the classical area for researching space learning ability,and most possibly be impaired in stress.Its pathophysiological change is the material base for the impairment of space learning ability.Preexperiment suggested that the independent breath wasn't inhibited and hemodynamics was stable when rats inhaled 1.0MAC sevoflurane.Obal D et al presented a study with the same results.Moris maze or Y—maze is usually used to measure the impairment of space learning ability in the past experiment.In our study,the rats undergone acute myocardial reperfusion were too weak to endure maze test.LTP is a classical index to study the plasticity of the nerve synapse related to learning memory.We assessed the space learning abilities of rats at synapse level by measure LTP in vivo.In our study,HO-1 expression in hippocampus of rats suffered from acute myocardial reperfusion injury was significantly high,which suggested hippocampus can be influenced by the oxidation stress caused by acute myocardial reperfusion injury. In the 1^st,3^rdday,LTP was inhibited,and no difference with the compared group in the 7^thday,which suggested brief impairment of space learning ability after acute myocardial reperfusion.The inflammatory cytokine TNF-αmRNA,IL-1βmRNA and IL-1βprotein expression increased.The expression of TNF-αmRNA,IL-1βmRNA and IL-1βwas simultaneous with the change of LTP.We presumed that in the acute myocardial reperfusion injury rats,the expression increase of inflammatory cytokine in hippocampus was relative to the brief impairment of space learning ability.ConclusionAcute myocardial reperfusion injury can impair the space learning ability in rats, and the increases of TNF-αmRNA,IL-1βmRNA and IL-1βin hippocampus may play roles in its mechanism.Sevoflurane precondition can lessen myocardia reperfusion injury.