Evaluation of Rapid Ischemic Preconditioning in a Rabbit Model of Spinal Cord Ischemia

Background: Rapid ischemic preconditioning (IPC) has been shown to reduce cellular injury after subsequent cardiac and cerebral ischemia. However, the data on rapid IPC of the spinal cord is limited. The authors investigated whether pretreatment with sublethal ischemia of spinal cord can attenuate neuronal injury after spinal cord ischemia in rabbits.

Methods: Forty-seven male New Zealand white rabbits were randomly assigned to one of three groups (n = 15 or 16 each). In the IPC(-) group, the infrarenal aorta was occluded for 17 min to produce spinal cord ischemia. In the IPC(+) group, 5 min of aortic occlusion was performed 30 min before 17 min of spinal cord ischemia. In the sham group, the aorta was not occluded. Hind limb motor function was assessed at 3 h, 24 h, 4 days, and 7 days after reperfusion using Tarlov scoring (0 = paraplegia; 4 = normal). Animals were killed for histopathologic evaluation at 24 h or 7 days after reperfusion. The number of normal neurons in the anterior spinal cord (L4-L6) was counted.

Results: Neurologic scores were significantly higher in the IPC(+) group than the IPC(-) group at 3 and 24 h after reperfusion (P < 0.05). However, neurologic scores in the IPC(+) group gradually decreased and became similar to those in the IPC(-) group at 4 and 7 days after reperfusion. At 24 h after reperfusion, the numbers of normal neurons were significantly higher in the IPC (+) group than in the IPC(-) group (P < 0.05) and were similar between the IPC(+) and sham groups. At 7 days after reperfusion, there was no difference in the number of normal neurons between the IPC(+) and IPC(-) groups.     

缺血预处理对脊髓缺血损伤细胞内Ca2+变化的影响

目的　观察缺血预处理对脊髓缺血损伤细胞内 Ca2 变化的影响。　方法　将 44只健康新西兰大白兔随机分为三组 :缺血组 2 0只 ,缺血预处理组 2 0只 ,假手术组 4只。缺血组于左肾动脉下夹闭腹主动脉 40分钟后开放灌注 ;缺血预处理组夹闭腹主动脉 5分钟 ,开放 15分钟 ,再次夹闭 40分钟后开放再灌注 ;假手术组动物手术操作同缺血组 ,但不夹闭腹主动脉。分别于夹闭 40分钟后即刻、开放再灌注 2小时、8小时、2 4小时和 72小时各时相点测定脊髓组织 Ca2 含量 ,并评定、记录动物后肢神经功能。　结果　缺血预处理组脊髓组织 Ca2 显著低于缺血组各时相值 ;再灌注 8小时后神经功能评分缺血预处理组明显高于缺血组 (P<0 .0 1)。　结论　缺血预处理具有降低神经元胞浆游离 Ca2 浓度 ,防止Ca2 超载 ,稳定细胞内环境的能力 ,对主动脉阻断所致的脊髓缺血损伤有良好的保护作用。其表现为明显降低瘫痪发生率 ,增加术后神经评分     

Effect of ischemic post-conditioning on spinal cord ischemic-reperfusion injury in rabbits

OBJECTIVES: To investigate the potential protective effect of ischemic post-conditioning (Post-con) on ischemia-reperfusion injury of the rabbit spinal cord, and to determine if there is an additive neuroprotective effect when ischemic preconditioning (IPC) and Post-con are combined. METHODS: Forty New Zealand white rabbits were randomly divided into four groups: group Control (C; n=10), aortic occlusion (AOC; for 30 min; group IPC (n=10) three cycles of three-minute AOC plus three-minute reperfusion before the 30-min AOC; group Post-con (n=10), three cycles of three-minute reperfusion plus three-minute AOC immediately upon reperfusion after 30-min AOC; group IPC+Post-con (n=10), where animals were subjected to both IPC and Post-con. At six hours, 24 hr and 48 hr following reperfusion, neurological function was assessed according to Tarlov scores, and at 48 hr, the spinal cords were procured for the histopathologic evaluation, by comparing the number of intact alpha-motor neurons in the anterior horn. RESULTS: The median count (and quartiles) of intact alpha-motor neurons was greatest in group Post-con 73 (69-76) and group IPC+Post-con 29 (22-42) compared to the numbers of viable alpha-motor neurons in groups C 6 (4-9) and IPC 15 (11-18) (P < 0.001). The numbers of animals who developed paraplegia according to Tarlov criteria were 7/10 in groups Post-con and IPC+Post-con, compared to 9/10 animals in each of groups C and IPC. CONCLUSIONS: This laboratory investigation provides histological evidence that Post-con may protect the spinal cord from moderate to severe ischemia reperfusion injury. Ischemic preconditioning conferred no additional benefits in this rabbit model. The results have potential clinical implications for patients undergoing thoracoabdominal aortic reconstructive surgery.     

缺血预处理对兔主动脉阻断后脊髓一氧化氮、后肢神经功能和肌电图的影响

目的　探讨缺血预处理 (IPC)对缺血预处理对兔主动脉阻断后脊髓功能和一氧化氮(NO)的影响。方法　 2 4只日本大白兔随机分为假手术组 (A组 )、缺血再灌注组 (B组 )和IPC保护组 (C组 ) ,每组 8只。分别于首次预处理即刻 (C 40 )、缺血即刻 (I0 )、缺血 45min(I45)、再灌注后 60min(R60 )和术后 7d处死动物前即刻 (R7d)采血检测血清和R7d脊髓组织NO的浓度。术后观察后肢神经功能的评分、后肢针电极肌电图 (EMG)和脊髓组织病理学的改变。结果　缺血再灌注损伤后B组血清NO浓度较缺血前和A、C组对应时点值显著升高 (P <0 .0 1)。C组R7d血清NO浓度明显低于其他时点及A组R7d测定值 (P <0 .0 5或 0 .0 1)。B组脊髓组织NO浓度显著高于A、C组(P <0 .0 1)。B组后肢神经功能和脊髓病理学评分均显著性低于A、C组 (P <0 .0 5或 0 .0 1) ,其后肢EMG亦较C组有显著性病理改变 (P <0 .0 1)。结论　IPC对家兔主动脉阻断后脊髓缺血再灌注损伤有良好的保护作用 ,其保护作用机制与抑制NO的生成有关。     

Anesthetic preconditioning with sevoflurane does not protect the spinal cord after an ischemic-reperfusion injury in the rat

Anesthetic preconditioning (APC) is a protective mechanism, whereby exposure to a volatile anesthetic renders a tissue resistant to a subsequent ischemic insult. We hypothesized that APC of the rat spinal cord with sevoflurane would reduce neurologic deficit after an ischemic-reperfusion injury. Rats were randomly assigned to 1 of 5 groups. The ischemic preconditioning (IPC) group (n = 14) had 3 min of IPC, 30 min of reperfusion, and 12 min of ischemia. The chronic APC (cSEVO) group (n = 14) had 1 h of APC with 3.5% sevoflurane on each of 2 days before ischemia. The acute APC (aSEVO) group (n = 14) had 1 h of APC with 3.5% sevoflurane followed by a 1-h washout period before the induction of ischemia. The controls (n = 14) underwent no preconditioning before ischemia. IPC attenuated the ischemia-reperfusion injury, whereas aSEVO and cSEVO groups were no better than control animals. Histologic evaluation of the spinal cord showed severe neurologic damage in all groups except for the IPC group and sham-operated rats. APC with sevoflurane did not reduce neurologic injury in a rat model of spinal cord ischemia. Traditional ischemic preconditioning had a strong protective benefit on neurologic outcome.     

芦荟多糖对脊髓缺血损伤的神经保护作用

目的:探讨芦荟多糖(aloe polysaccharide,AP)对兔脊髓缺血损伤是否有神经保护作用.方法:32只成年雄性新西兰兔随机分成4组(每组8只 ),即对照组(C 组)、芦荟多糖组(A组)、溶剂对照组( V组 ) 及假手术组(S组).A组在脊髓缺血前30min经耳缘静脉给予50m·kg-1芦荟多糖;V组以同样方式给予等容量生理盐水;C组仅仅制备脊髓缺血损伤模型,不进行其它处理;S组仅仅暴露腹主动脉,而不阻断它,其他处理同C组;兔脊髓缺血模型采用夹闭兔腹主动脉肾下段20min.再灌注后48h,对所有动物神经功能评分,然后处死动物取脊髓(L5-7),制作标本行组织病理学观察.结果:A组的神经功能评分和脊髓前角正常神经细胞数明显多于C组及V组(P<0.01);C组及V组的神经功能评分和脊髓前角正常神经细胞数组间无明显差异(P>0.05);神经功能评分与其对应脊髓前角正常神经细胞计数之间有显著相关性(r=0.804,P<0.01).结论:芦荟多糖对兔脊髓缺血再灌注损伤有明显的神经保护作用.     

羟乙基淀粉行急性等容血液稀释对兔脊髓缺血-再灌注损伤的保护作用

目的 探讨用羟乙基淀粉(HES130/0.4)急性等容血液稀释(ANH)对兔脊髓缺血-再灌注损伤的保护作用.方法 24只新西兰雄性大白兔,随机均分成三组:HES组,生理盐水组(NS组),对照组(C组).HES组和NS组分别用HES130/0.4和生理盐水行ANH,使红细胞压积(Hct)达30%.ANH的方法为:15 min内经股动脉恒速放出计算的血量,同时利用微量输液泵经静脉输注与放血量等量的液体(HES组)或输注3倍于放血量的液体(NS组),放血和输液速度相等,维持术中大白兔的血压和心率恒定.稳定15 min后,行肾下腹主动脉(IRA)阻闭建立脊髓缺血-再灌注损伤模型.分别于稀释前、稀释后和腹主动脉开放后采集动脉血进行血气分析.评估再灌注后4、8、12、24及48 h后肢运动功能,并于48 h处死动物取脊髓(L5)制标本行病理组织学观察.结果 再灌注后48 h.HES组和NS组动物的后肢运动功能比C组明显改善(P＜0.05或P＜0.01);HES组和NS组动物脊髓前角正常运动神经元计数比C组显著增加(P＜0.05或P＜0.01),但两组间差异无统计学意义.结论 HES130/0.4行适度ANH对脊髓缺血-再灌注损伤具有显著地保护作用.     

The effect of thalidomide on spinal cord ischemia/reperfusion injury in a rabbit model

STUDY DESIGN: Randomized study. OBJECTIVES: To evaluate the effects of thalidomide on spinal cord ischemia/reperfusion injury via reduced TNF-alpha production. SETTING: Animal experimental laboratory, Clinical Research Institute of Seoul National University Hospital, Seoul, Korea. METHODS: Spinal cord ischemia was induced in rabbits by occluding the infrarenal aorta. Rabbits in group N did not undergo ischemic insult, but rabbits in groups C (the untreated group), THA, and THB underwent ischemic insult for 15 min. The THA and THB groups received thalidomide (20 mg/kg) intraperitoneally (i.p.) before ischemia, but only the THB group received thalidomide (i.p., 20 mg/kg) after 24 and 48 h of reperfusion. After evaluating neurologic functions at 1.5 h, 3, and 5 days of reperfusion, rabbits were killed for histopathologic examination and Western blot analysis of TNF-alpha. RESULTS: The THA and THB groups showed significantly less neurologic dysfunction than the C group at 1.5 h, 3, and 5 days of reperfusion. The number of normal spinal motor neurons in ventral gray matter was higher in THA and THB than in C, but no difference was observed between THA and THB. Western blot analysis showed a significantly higher level of TNF-alpha in C than in THA and THB at 1.5 h of reperfusion, but no difference was observed between C, THA, or THB at 3 or 5 days of reperfusion. CONCLUSION: Thalidomide treatment before ischemic insult reduces early phase ischemia/reperfusion injury of the spinal cord in rabbits.     

Long-term assessment of hind limb motor function and neuronal injury following spinal cord ischemia in rats

Recent evidence suggests that brain injury caused by ischemia is a dynamic process characterized by ongoing neuronal loss for at least 14 days after ischemia. However, long-term outcome following spinal cord ischemia has not been extensively examined. Therefore, we investigated the changes of hind limb motor function and neuronal injury during a 14-day recovery period after spinal cord ischemia. Male Sprague-Dawley rats received spinal cord ischemia (n = 64) or sham operation (n = 21). Spinal cord ischemia was induced by inflation of a 2F Fogarty catheter placed into the thoracic aorta for 6, 8, or 10 minutes. The rats were killed 2, 7, or 14 days after reperfusion. Hind limb motor function was assessed with the 21-point Basso, Beattie, and Bresnahan (BBB) scale during the recovery period. The number of normal and necrotic neurons was counted in spinal cord sections stained with hematoxylin/eosin. Longer duration of spinal cord ischemia produced severer hind limb motor dysfunction at each time point. However, BBB scores gradually improved during the 14-day recovery period. Neurologic deterioration was not observed between 7 and 14 days after reperfusion. The number of necrotic neurons peaked 2 days after reperfusion and then decreased. A small number of necrotic neurons were still observed 7 and 14 days after reperfusion in some of the animals. These results indicate that, although hind limb motor function may gradually recover, neuronal loss can be ongoing for 14 days after spinal cord ischemia.     

Effects of xenon on ischemic spinal cord injury in rabbits: a comparison with propofol

Background: Xenon has been shown to reduce cellular injury after cerebral ischemia. However, the neuroprotective effects of xenon on ischemic spinal cord are unknown. The authors compared the effects of xenon and propofol on spinal cord injury following spinal cord ischemia in rabbits. Methods: Thirty‐two male New Zealand white rabbits were randomly assigned to one of three groups. In the xenon and propofol group, 70% of xenon and 0.8 mg/kg/min of propofol were administered 30 min before an aortic occlusion and maintained until the end of the procedure. The aortic occlusion was performed for 15 min. In the sham group, the aorta was not occluded. After an assessment of the hind limb motor function using the Tarlov score (0=paraplegia, 4=normal) at 48 h after reperfusion, gray and white matter injuries were evaluated based on the number of normal neurons in the anterior spinal cord and the percentage areas of vacuolation in the white matter, respectively. Results: In the xenon and propofol groups, the Tarlov score and the number of normal neurons were significantly lower than those in the sham group, whereas the percentage areas of vacuolation were similar among the three groups. There were no significant differences in Tarlov scores and the number of normal neurons between the xenon and the propofol groups. Conclusion: The results indicated that 70% of xenon has no additional neuroprotective effects on ischemic spinal cord injury in rabbits compared with propofol.     

Ischemic preconditioning reduces neurologic injury in a rat model of spinal cord ischemia.

BACKGROUND: Ischemic preconditioning (IPC) is an endogenous cellular protective mechanism whereby brief, noninjurious periods of ischemia render a tissue more resistant to a subsequent, more prolonged ischemic insult. We hypothesized that IPC of the spinal cord would reduce neurologic injury after experimental aortic occlusion in rats and that this improved neurologic benefit could be induced acutely after a short reperfusion interval separating the IPC and the ischemic insult. METHODS: Forty male Sprague-Dawley rats under general anesthesia were randomly assigned to one of two groups. The IPC group (n = 20) had 3 minutes of aortic occlusion to induce spinal cord ischemia 30 minutes of reperfusion, and 12 minutes of ischemia, whereas the controls (n = 20) had only 12 minutes of ischemia. Neurologic function was evaluated 24 and 48 hours later. Some animals from these groups were perfusion-fixed for hematoxylin and eosin staining of the spinal cord for histologic evaluation. RESULTS: Survival was significantly better at 48 hours in the IPC group. Sensory and motor neurologic function were significantly different between groups at 24 and 48 hours. Histologic evaluation at 48 hours showed severe neurologic damage in rats with poor neurologic test scores. CONCLUSIONS: Ischemic preconditioning reduces neurologic injury and improves survival in a rat model of spinal cord ischemia. The protective benefit of IPC is acutely invoked after a 30-minute reperfusion interval between the preconditioning and the ischemic event.     

缺血预处理对大鼠肺组织中缺血再灌注损伤相关基因表达的影响

目的 探讨缺血预处理(IPC)后大鼠肺组织中缺血再灌注损伤(IRI)相关基因的表达,为研究IPC减轻IRI的分子机制提供依据.方法 将雄性Wistar大鼠随机分为三组,缺血预处理组(IPC组,n:20)阻断左肺门5 min,开放10 min,如此重复3次,然后阻断左肺门,1 h后恢复血流灌注;缺血再灌注组(IR组,n=20)直接阻断左肺门,1 h后开放血流;假手术组(n=5)仅松解肺下部韧带,不做其它处理.IPC组和IR组分别于再灌注后1、3、6及24 h各取大鼠5只,切取左肺组织,采用含有22 226个大鼠基因点的Illumina RatRef-12全基因组表达谱微珠芯片检测肺组织中基因表达情况,比较IPC组与IR组各再灌注时间点基因表达的差异.结果 与IR组再灌注1 h相比,IPC组再灌注1 h时有1849个基因表达发生改变,其中上调的有918个,下调的有931个.与IR组再灌注3 h相比,IPC组再灌注3 h时有2568个基因表达发生改变,其中上调的有1377个,下调的有1191个.与IR组再灌注6 h相比,IPC组再灌注6 h时有1370个基因表达发生改变,其中上调的有563个,下调的有807个.与IR组再灌注24 h相比,IPC组再灌注24 h时仅有77个基因表达发生改变,全部为下调.结论 IPC对缺血再灌注损伤肺组织中基因表达的影响主要在再灌注后6 h内,以3 h最为明显;IPC可能通过影响凋亡相关基因、氧化应激相关基因、炎症反应及循环相关基因、能量代谢相关基因的表达来减轻IRI.     

不同高压氧预处理方案对兔脊髓缺血再灌注损伤的影响

目的 探讨不同高压氧预处理方案对兔脊髓缺血再灌注损伤的影响.方法 新西兰大白兔45只,月龄4～5月,体重2.0～2.5 kg,随机分为5组:假手术组(S组,n=5)开腹剥离左肾动脉下段腹主动脉但不阻断血流,20 min后关腹;脊髓缺血再灌注组(IR组,n=10)采用左肾动脉下段腹主动脉阻断法建立脊髓缺血再灌注损伤模型,缺血20 min后恢复灌注;不同方案高压氧预处理组(H_(1～3)组,n=10)分别接受连续5 d(H_1组)、10 d(H_2组)或20 d(H_3组)高压氧预处理(2.5 ATA,吸入氧浓度100%),1h/d,末次高压氧预处理结束后24 h时,建立脊髓缺血再灌注模型.再灌注48 h时,采用修正Tarlov评分,评价后肢运动功能.然后取L_5脊髓节段,分别行HE、TUNEL和nuoro-Jade B染色,计数脊髓正常神经元、凋亡神经元和变性神经元.结果 与S组比较,IR组后肢运动功能评分和脊髓前角正常神经元计数降低(P<0.01);与IR组比较,H_1组和H_2组后肢运动功能评分和脊髓前角正常神经元计数升高,凋亡神经元计数和变性神经元计数降低(JP<0.01),H_3组各指标差异无统计学意义(P>0.05);H_1组和h_2组各指标比较差异无统计学意义(P>0.05);与H_1组和H_2组比较,H_3组后肢运动功能评分和脊髓前角正常神经元计数降低,凋亡神经元计数和变性神经元计数升高(P<0.01).结论 连续5 d或10 d高压氧预处理(2.5 ATA,吸入氧浓度100%)可减轻脊髓缺血再灌注损伤;而连续20 d高压氧预处理无神经保护作用.     

The effects of N(G)-nitro-L-arginine-methyl ester on neurologic and histopathologic outcome after transient spinal cord ischemia in rabbits.

Little is known about the role of nitric oxide in the pathophysiology of spinal cord ischemia. We evaluated the effects of nitric oxide synthase (NOS) inhibition by N(G)-nitro-L-arginine-methyl ester (L-NAME) in rabbits whose abdominal aorta was occluded for 20 min (Experiment 1) or 25 min (Experiment 2). In Experiment 1, the L-NAME group (n = 6) received 3 mg/kg i.v. L-NAME, followed by an i.v. infusion of 3 mg x kg(-1). h(-1) until 6 h after reperfusion. Ischemia was induced 20 min after the start of L-NAME. The phenylephrine group (n = 6) received phenylephrine to maintain comparable blood pressure. The control group (n = 6) received saline. In Experiment 2, L-NAME (3 mg/kg i.v. L-NAME, followed by an i.v. infusion of 3 mg x kg(-1). h(-1) until 6 h after reperfusion) and phenylephrine groups (n = 6 each) were studied. Ischemia was induced 100 min after the start of L-NAME. Forty-eight hours after reperfusion, hindlimb motor function and histopathology of the spinal cord were examined. In Experiment 1, L-NAME and phenylephrine both improved neurologic outcome, with higher intraischemic blood pressures than saline. In Experiment 2, L-NAME worsened the neurologic and histopathologic outcome compared with phenylephrine. Attenuation of damage by L-NAME in Experiment 1 may be attributable to an intraischemic blood pressure increase. The worse outcome with L-NAME in Experiment 2 suggests that NOS inhibition exacerbates ischemic spinal cord damage. IMPLICATIONS: Nonselective inhibition of nitric oxide synthase activity has aggravating effects on the neurologic and histopathologic outcome after transient spinal cord ischemia.     

The temporal profile of the reaction of microglia,astrocytes, and macrophages in the delayed onset paraplegia after transient spinal cord ischemia in rabbits

In the present study, we sought to elucidate the temporal profile of the reaction of microglia, astrocytes, and macrophages in the progression of delayed onset motor dysfunction after spinal cord ischemia (15 min) in rabbits. At 2, 4, 8, 12, 24, and 48 h after reperfusion (9 animals in each), hind limb motor function was assessed, and the lumbar spinal cord was histologically examined. Delayed motor dysfunction was observed in most animals at 48 h after ischemia, which could be predicted by a poor recovery of segmental spinal cord evoked potentials at 15 min of reperfusion. In the gray matter of the lumbar spinal cord, both microglia and astrocytes were activated early (2 h) after reperfusion. Microglia were diffusely activated and engulfed motor neurons irrespective of the recovery of segmental spinal cord evoked potentials. In contrast, early astrocytic activation was confined to the area where neurons started to show degeneration. Macrophages were first detected at 8 h after reperfusion and mainly surrounded the infarction area later. Although the precise roles of the activation of microglia, astrocytes, and macrophages are to be further determined, the results indicate that understanding functional changes of astrocytes may be important in the mechanism of delayed onset motor dysfunction including paraplegia. IMPLICATIONS: Microglia and macrophages play a role in removing tissue debris after transient spinal cord ischemia. Disturbance of astrocytic defense mechanism, breakdown of the blood-spinal cord barrier, or both seemed to be involved in the development of delayed motor dysfunction.     

钙蛋白酶抑制剂对缺血再灌注损伤脊髓的保护作用

目的 观察大鼠脊髓缺血再灌注损伤后应用钙蛋白酶特异性抑制剂E-64-D,对脊髓神经细胞组织学改变和凋亡的影响及对大鼠后肢运动功能的保护作用.方法 选用纯种雄性成年SD大鼠106只,夹闭右肾动脉分支下腹主动脉30 min,再灌注即刻静脉应用钙蛋白酶特异性抑制剂E-64-D,观察再灌注后3、24、72 h和7 d脊髓损伤节段神经细胞的凋亡及再灌注后24、72h组织病理学改变;对再灌注后72 h的大鼠后肢功能进行评分.结果 脊髓缺血再灌注24 h开始出现神经细胞凋亡现象,脊髓组织出现病理学改变,神经元死亡,胶质细胞增生.应用E-64-D后,凋亡现象和细胞坏死得到抑制,差异有统计学意义(P<0.01).再灌注后72 h后肢功能也得到一定程度的保护.结论 脊髓再灌注损伤后静脉应用E-64-D治疗,可以明显抑制脊髓神经细胞的凋亡,有利于神经元的存活,损伤后3 d大鼠后肢运动功能得到一定程度的改善.     

Effect of puerarin on neural function and histopathological damages after transient spinal cord ischemia in rabbits

Ischemicspinalcordinjuryremainsadisastrouscomplicationofthedescendingandthoracoabdominalaortaeafteroperation .Thereportedincidenceofparaplegiarangesfrom 4 %to 33% .1Therefore ,agreatnumberofeffortshavebeenfocusedonsolvingthisproblem ,whichincludehypothermia ,cerebrospinalfluiddrainage ,temporarybypassandpharmacologicalagents .2 Thecellularandmolecularmechanismsofischemicspinalcordinjuryhavenotbeentotallyelucidated .Butvariousstudieshavesuggestedthatfreeradicalproduction ,calciumaccumulationand…     

腹主动脉局部灌注丙泊酚减轻脊髓缺血-再灌注损伤的研究

目的 建立兔脊髓缺血-再灌注损伤模型,研究经腹主动脉局部灌注丙泊酚对脊髓缺血-再灌注损伤的作用。方法 新西兰大耳白兔30只,随机均分为A、B、C三组,诱导后气管插管,持续监测平均动脉压、心率、脉搏血氧饱和度及肛温。左股动脉切开置管至腹主动脉分出左肾动脉远端1．0cm处,于左肾动脉开口远端0．5cm处阻断腹主动脉,同时阻断双侧髂总动脉,自阻断即刻开始经置入导管分别向阻断的腹主动脉远端灌注5ml／kg丙泊酚溶液（A组）、10％脂肪乳（B组）和生理盐水（C组）,30min后开放。于动物完全清醒即刻、再灌注后6、24和48h对双后肢神经功能进行评分,光镜观察脊髓前角正常运动神经元并计数。结果 清醒即刻、再灌注后6、24和48hA组神经行为学评分明显高于B和C组（P〈0．05）,B、C两组比较差异无统计学意义。三组脊髓前角正常运动神经元中位数分别为11、1和0,A组明显高于B、C两组（P〈0．05）。结论 腹主动脉阻断期间经阻断的腹主动脉局部灌注丙泊酚可减轻脊髓缺血一再灌注损伤。     

ROS和PI3K-Akt在缺血后处理或控制性低压灌注减轻大鼠脊髓缺血再灌注损伤中的作用

目的 探讨活性氧自由基(ROS)和磷酸酰肌醇3激酶-蛋白激酶B(PI3K-Akt)在缺血后处理或控制性低压灌注减轻大鼠脊髓缺血再灌注损伤中的作用.方法 雄性SD大鼠126只,体重300～350 g,随机分为7组(n=18),缺血再灌注组(I/R组)阻断胸主动脉同时维持MAP40 mm Hg持续9 min进行脊髓缺血,胸主动脉开放后使MAP升至100 mm Hg进行脊髓再灌注;缺血后处理组(IP组)开放主动脉后,进行再灌注30 s缺血30 s,重复3次,同时维持MAP 100 mm Hg;控制性低压灌注组(LR)开放主动脉后维持MAP 40 mm Hg持续5 min后升高至100 mm Hg;缺血后处理+PI3K抑制剂LY-294002组(IP+L组)和控制性低压灌注+LY-294002组(LR+L组)分别于实施缺血后处理和控制性低压后立即动脉注射LY-294002 25 mg/kg;缺血后处理+氧自由基清除剂N-乙酰半胱氨酸组(IP+N组)和控制性低压灌注+N-乙酰半胱氨组(LR+N组)分别于实施缺血后处理和控制性低血压后立即动脉注射N-乙酰半胱氨酸100 mg/kg.于再灌注2 h时,各组处死12只大鼠,取腰段脊髓组织,测定胞浆Akt磷酸化水平和线粒体通透性转换孔(mPTP)开放程度.分别于再灌注4、12、24、48 h进行神经行为学评分,然后处死大鼠,取腰段脊髓组织,分别进行脊髓前角正常神经元和凋亡神经元的计数.结果 与I/R组比较,IP组和LR组Akt磷酸化水平升高,mPTP开放程度和神经元凋亡计数降低,神经行为学评分和正常神经元计数升高(P＜0.01);IP组与LR组各指标比较差异无统计学意义(P＞0.05).LY294002和N-乙酰半胱氨酸均可逆转缺血后处理和控制性低压灌注对脊髓的保护作用,引起mPTP开放程度升高(P＜0.01).结论 ROS激活PI3K-Akt进而降低线粒体通透性是缺血后处理或控制性低压灌注减轻大鼠脊髓缺血再灌注损伤的机制.     

The time course of acquisition of ischemic tolerance and induction of heat shock protein 70 after a brief period of ischemia in the spinal cord in rabbits

We examined the time course of development of ischemic tolerance in the spinal cord and sought its mechanism exploring the expression of heat shock protein 70 (HSP70). Spinal cord ischemia was produced in rabbits by occlusion of the abdominal aorta. In Experiment 1, neurologic and histopathologic outcome was evaluated 48 h after prolonged ischemia (20 min) that was given 2 days, 4 days, or 7 days after a short period of ischemia (ischemic pretreatment) sufficient to abolish postsynaptic component of spinal cord evoked potentials. Control animals were given prolonged ischemia 4 days after sham operation. In Experiment 2, HSP70 expression in motor neurons after pretreatment without exposure to prolonged ischemia was examined by immunohistochemical staining. Ischemic pretreatment 4 days (but not 2 days or 7 days) before 20 min ischemia exhibited protective effects against spinal cord injury. In the cytoplasm, HSP70 immunoreactivity was mildly increased after 2, 4, and 7 days of ischemic pretreatment. However, the incidence of nuclear HSP70 immunoreactivity 2 days, 4 days, and 7 days after ischemic pretreatment was 2 of 6 animals, 4 of 6 animals, and 1 of 6 animals, respectively (none in the control group). These results suggest that ischemic tolerance is apparent 4 days after ischemic pretreatment and that HSP70 immunoreactivity in the nucleus may provide some insight into the mechanisms of ischemic tolerance in the spinal cord.