大鼠心肌缺血再灌注损伤的中枢神经调节机制:下丘脑室旁核神经元兴奋性

Central nervous regulatory mechanism of myocardial ischemia-reperfusion injury in rats:excitability of neurons in hypothalamic paraventricular nucleus

目的评价下丘脑室旁核(PVN)神经元兴奋性与心肌缺血再灌注损伤时中枢神经调节机制的关系。方法清洁级健康成年雄性SD大鼠,6~8周龄,体重260~300g,取PVN置管成功的24只大鼠,采用随机数字表法分为4组(n=6):假手术组(S组)、心肌缺血再灌注组(I/R组)、γ-氨基丁酸组(GABA组)和L-谷氨酸组(L-Glu组)。采用结扎冠状动脉左前降支30min再灌注120min的方法制备心肌缺血再灌注损伤模型。S组和I/R组于心肌缺血前10min经PVN导管微量输注生理盐水2.4μl/h,持续50min;GABA组和L-Glu组分别于心肌缺血前10min经PVN导管微量输注30μmol/LGABA或30μmol/LL-Glu,速度2.4μl/h,持续50min。于心肌缺血前10min(T0)、心肌缺血开始(T1)、缺血30min(T2)及再灌注120min(T3)时记录HR和MAP,计算心率血压乘积(RPP)。T3时取血样,采用化学发光法测定血浆cTnI浓度。随后处死大鼠,取心肌组织,检测心肌梗死体积(IS)和IS/缺血危险区体积(AAR)百分比;取PVN组织,采用Westernblot法检测c-fos的表达。结果S组未见心肌梗死发生,其余3组心肌梗死明显。与S组比较,I/R组、GABA组和L-Glu组血浆cTnI浓度升高,PVNc-fos表达上调,I/R组和GABA组T1-3时、L-Glu组T3时HR、MAP及RPP降低(P<0.05);与I/R组比较,GABA组IS、IS/AAR百分比、血浆cTnI浓度降低,PVNc-fos表达下调,T1,2时HR、MAP及RPP降低,L-Glu组IS、IS/AAR百分比、血浆cTnI浓度升高,PVNc-fos表达上调,T1,2时HR、MAP及RPP升高(P<0.05)。结论PVN神经元兴奋性参与了大鼠心肌缺血再灌注损伤的中枢神经调节机制:兴奋性降低可减轻损伤,兴奋性升高则加重损伤。

Objective To evaluate the relationship between excitability of neurons in hypothalamic paraventricular nucleus(PVN)and central nervous regulatory mechanism of myocardial ischemia-reperfusion(I/R)injury in rats.Methods Clean-grade healthy adult male Sprague-Dawley rats,in which PVN catheters were successfully implanted,aged 6-8 weeks,weighing 260-300 g,were divided into 4 groups(n=6 each)using a random number table method:sham operation group(S group),myocardial I/R group(I/R group),γ-aminobutyric acid group(GABA group)and L-glutamic acid group(L-Glu group).Myocardial ischemia was induced by occlusion of the left anterior descending coronary artery for 30 min followed by 120-min reperfusion.Normal saline 2.4 μl/h was infused for 50 min via the PVN catheter starting from 10 min before ischemia in S and I/R groups.GABA 30 μmol/L and L-glutamic acid 30 μmol/L were infused for 50 min via the PVN catheter at a rate of 2.4 μl/h starting from 10 min before ischemia in GABA and L-Glu groups.The heart rate(HR)and mean arterial pressure(MAP)were recorded at 10 min before ischemia(T0),beginning of ischemia(T1),30 min of ischemia(T2)and 120 min of reperfusion(T3).Rate-pressure product(RPP)was calculated.Blood samples were collected at T3 for determination of plasma cardiac troponin I(cTnI)concentrations by chemiluminescence assay.Rats were then sacrificed and myocardial specimens were obtained for measurement of myocardial infarct size(IS)and area at risk(AAS),and IS/AAR percentage was calculated.PVN tissues were taken to detect the expression of c-fos by Western blot.Results No myocardial infarction was found in group S,and myocardial infarction was marked in the other three groups.Compared with group S,the plasma cTnI concentrations were significantly increased,and the expression of c-fos in PVN was up-regulated in I/R,GABA and L-Glu groups(P<0.05),and MAP,HR and RPP were significantly decreased at T1-3 in I/R and GABA groups and at T3 in group L-Glu(P<0.05).Compared with group I/R,IS and IS/AAR percentage were significantly decreased,the plasma cTnI concentrations were decreased,the expression of c-fos in PVN was down-regulated,and HR,MAP and RPP were decreased at T1,2 in group GABA,and IS and IS/AAR percentage were significantly increased,the plasma cTnI concentrations were increased,the expression of c-fos in PVN was up-regulated,and HR,MAP and RPP were increased at T1,2 in group L-Glu(P<0.05).Conclusion Excitability of neurons in hypothalamic PVN is involved in central nervous regulatory mechanism of myocardial I/R injury in rats:decreased excitability can attenuate myocardial I/R injury and increased excitability aggravates myocardial I/R injury.