Propofol prevents delayed neuronal death following transient forebrain ischemia in gerbils

PURPOSE: This study was conducted to ascertain whether propofol may protect against delayed neuronal death in the hippocampal CA1 subfield in gerbils. METHODS: Thirty-five gerbils were randomly assigned to five groups: Group I, the control group, a sham operation treated with physiological saline solution (PSS); Group II, ischemia/reperfusion treated with PSS; Group III, ischemia/reperfusion treated with 50 mg x kg(-1) propofol; Group IV, ischemia/reperfusion treated with 100 mg x kg(-1) propofol; Group V ischemia/reperfusion treated with 150 mg x kg(-1) propofol. Transient forebrain ischemia was induced by occluding the bilateral common carotid arteries for four minutes under N2O/O2/halothane anesthesia after administration of propofol or PSS. Five days later, histopathological changes in the hippocampal CA1 subfield were examined using a light microscope and degenerative ratio of the pyramidal cells were measured according to the following formula: (number of degenerative pyramidal cell/total number of pyramidal cells per 1 mm of hippocampal CA1 subfield) x 100. RESULTS: In group II, the pyramidal cells were atrophic and pycnotic; vacuolation and structural disruption of the radial striated zone was observed. In the other four groups, these changes were not observed. The degenerative ratios of pyramidal cells were as follows; group I: 5.9 +/- 1.9%, group II: 94.6 +/- 2.5% (P < 0.01), group III: 10.7 +/- 1.7%, group IV: 9.7 +/- 1.8%, group V: 9.2 +/- 1.9%. CONCLUSION: This study suggests that propofol may prevent delayed neuronal death in the hippocampal CA1 subfield after cerebral ischemia/reperfusion in gerbils.     

Influence of rewarming conditions after hypothermia in gerbils with transient forebrain ischemia.

OBJECT: Recently, several studies have demonstrated that hypothermia has a beneficial effect on clinical outcome; however, it is difficult to determine the appropriate rewarming conditions in clinical use. The purpose of the present study was to examine the influence of rewarming conditions in gerbils with transient forebrain ischemia. METHODS: Ischemia was induced in the gerbils by a 5-minute bilateral common carotid artery occlusion, after which the animals were immediately subjected to moderate or deep hypothermia. After moderate hypothermia (30.5 degrees C for 4 hours) the animals were rewarmed over standard, fast, or slow time periods. After deep hypothermia (24 degrees C for 2 hours) the animals were rewarmed in a standard, fast, slow, or stepwise manner. Cerebral blood flow (CBF), extracellular glutamate, and lactate were monitored. Hippocampal CA I cell damage was assessed 7 days after induction of ischemia. In animals treated with moderate hypothermia, the rewarming rate had no influence on the number of surviving neurons. However, fast rewarming from deep hypothermia (to 37 degrees C for 30 minutes) failed to provide the neuroprotective effect of hypothermia. Furthermore, this group showed a poor recovery of CBF (p < 0.01) and, consequently, an increase in extracellular glutamate (p < 0.01) and lactate (p < 0.01) in the hippocampus. CONCLUSIONS: The results of this study indicate a transient uncoupling of CBF and cerebral metabolism during fast rewarming from deep hypothermia, whereas slow and stepwise rewarming periods were found to be useful for protection against uncoupling of CBF and cerebral metabolism during rewarming.     

Neuronal damage in gerbils caused by intermittent forebrain ischemia.

OBJECT: The purpose of this study was to investigate the possibility of preventing cumulative neuronal damage after repetitive severe ischemia. METHODS: The authors monitored ischemic depolarization in the gerbil hippocampus, which has recently been shown to be a good experimental model of the effects of brief ischemia on the brain, and evaluated neuronal damage in the CA1 subregion 7 days after the ischemic insult. In a single-ischemia paradigm, the results indicate that induction of ischemia-induced neuronal damage depended on the duration of ischemic depolarization. Neuronal damage can be detected in the CA1 subregion after a period of depolarization lasting 210 seconds. Using a double-ischemia paradigm in which the animals were subjected to two periods of ischemia, there was apparently no accumulation of neuronal damage from the first ischemic episode to the second, provided the duration of the first period of ischemic depolarization did not exceed 90 seconds. Neuronal damage accumulated when the duration of the first ischemia episode exceeded 90 seconds, regardless of the duration of the reperfusion interval between the two ischemic insults. Finally, when the ischemic insult was spread over four separate episodes, each lasting 90 seconds (with a reperfusion interval of 5 minutes), neuronal damage was not found when the total depolarization period was less than 420 seconds. CONCLUSIONS: The authors conclude that cumulative neuronal damage may be avoided by adopting an intermittent ischemia approach. The implications of these results for human surgery requiring temporary occlusion of the cerebral arteries are discussed.     

A new model of transient hindbrain ischemia in gerbils

A model of transient hindbrain ischemia in Mongolian gerbils is described. The vertebrobasilar junction of gerbils was exposed by a transcervical approach through the space between the atlas and occipital bone. The origin of the basilar artery was occluded by a clip, and the local cerebral blood flow (CBF) was measured with carbon-14-iodoantipyrine autoradiography. This gerbil model produces ischemia in the thalamus, midbrain, pons, medulla, and cerebellum, where blood flow is supplied from the vertebrobasilar system. Recirculation of blood flow was easily accomplished by removing the clip. Local CBF returned to normal levels immediately after recirculation, then decreased at 30 minutes after recirculation (postischemic hypoperfusion). Almost no effects of local CBF in the forebrain structures were noted during and after hindbrain ischemia. The model may be useful to study the pathophysiological, metabolic, and histopathological effects of ischemia in the vertebrobasilar system.     

Postischemic hypothermia inhibits the generation of hydroxyl radical following transient forebrain ischemia in rats

A small reduction of body temperature during reperfusion following cerebral ischemia has been known to ameliorate neuronal injury. However, the mechanisms underlying postischemic hypothermia-induced neuroprotection are poorly understood. The burst of reactive oxygen species (ROS) formation that occurs during reperfusion has been documented to be involved in ischemic neuronal degeneration. In this study, we investigated the effect of postischemic hypothermia on ROS production following transient forebrain ischemia using an in vivo microdialysis technique. Forebrain ischemia was induced by bilateral carotid artery occlusion combined with hemorrhagic hypotension for 20 min in male Wistar rats. The body temperature was kept at 37 degrees C during ischemia and controlled at either 32 degrees C or 37 degrees C after reperfusion. The amount of hydroxyl radical produced in striatum was evaluated by measurement of 2,3- and 2,5-dihydroxybenzoic acid (DHBA), which is generated by salicylate hydroxylation. We also measured the extracellular concentration of xanthine, while determining striatal blood flow by the hydrogen clearance technique. In animals whose postischemic body temperature was maintained at 37 degrees C, the levels of 2,3- and 2,5-DHBA significantly increased after reperfusion. The peak levels of 2,3- and 2,5- DHBA were 2.9-fold and 2.7-fold increased above the corresponding baseline values, respectively. Postischemic hypothermia completely inhibited the hydroxyl radical formation. Likewise, xanthine formation was also inhibited by postischemic hypothermia. In contrast, striatal cerebral blood flow was not altered by temperature modulation during reperfusion. These results suggest that inhibition of ROS production accompanied with suppression of xanthine formation is implicated in the neuroprotection of postischemic hypothermia.     

Superoxide dismutase prevents lipid peroxidation in burned patients

Animal models and human studies have shown that conjugated dienes rise in the plasma after thermal injury. These dienes may serve as a marker of oxygen radical-mediated tissue injury. Twelve burn patients were randomized to receive the antioxidant enzyme polyethylene glycolconjugated superoxide dismutase (PEG-SOD). Patients received either 500 or 1000 units per kilogram of PEG-SOD intravenously within 6 h of injury. Plasma samples were collected and conjugated diene levels were compared to diene levels of burn patients not treated and to diene levels from normal volunteers. Conjugated diene levels were increased in burn patients. PEG-SOD in either dose initially decreased conjugated diene levels in the plasma of both treatment groups. By 72 h the diene levels increased in the 500 unit/kg group, but remained at near control levels in the 1000 unit/kg group for up to 200 h after injury. These data suggest that PEG-SOD is capable of preventing conjugated dienes formed as the result of oxygen radical production. It appears that 1000 units/kg is more effective than 500 units/kg in preventing conjugated diene formation.     

瑞芬太尼预先给药对兔心肌缺血再灌注时脂质过氧化反应的影响

目的 评价瑞芬太尼预先给药对兔心肌缺血再灌注时脂质过氧化反应的影响.方法 家兔40只,雌雄不拘,体重1.5～2.5 kg,随机分为5组(n=8),Ⅱ组、Ⅲ组和V组采用静脉注射垂体后叶素2.5 U/kg的方法制备急性心肌缺血模型,Ⅰ组和Ⅳ组给予等容量生理盐水.Ⅲ组静脉注射吗啡3.3 mg/kg后30 min给予垂体后叶素前;Ⅳ组静脉输注瑞芬太尼3.3μg·kg-1·min-130 min时给予生理盐水;V组静脉输注瑞芬太尼3.3μg·kg-1·min-1 30 min时给予垂体后叶素.于给予垂体后叶素前即刻(T1)、给予垂体后叶素后24 h(T2)、48 h(T3)时采集颈内静脉血样,测定血清心肌肌钙蛋白I(cTnI)浓度.取心肌组织,测定超氧化物歧化酶(SOD)活性及丙二醛(MDA)含量.电镜下观察心肌组织超微结构.结果 与Ⅰ组比较,Ⅱ组血清cTnI浓度和心肌组织MDA含量升高,心肌组织SOD活性降低(P＜0.01);与Ⅱ组比较,Ⅲ组及V组血清cTnI浓度和MDA含量降低,心肌组织SOD活性升高(P＜0.05或0.01).电镜下Ⅴ组心肌损伤程度轻于Ⅱ组.结论瑞芬太尼预先给药可抑制脂质过氧化反应,从而减轻兔心肌缺血再灌注损伤.     

JNK在沙土鼠脑缺血预处理中的作用及机制

Kitagawa等[1]在沙土鼠脑缺血的实验研究中,首次观察到机体对短暂亚致死性缺血的适应性反应能增加神经元对致死性缺血的耐受性,由此提出了脑缺血预处理(ischemic preconditioning,IP)的概念。此后各国学者对IP的机制进行了广泛的研究,提出了许多假说。近年来,以受体激活为起点,     

Propofol attenuates myocardial lipid peroxidation during coronary artery bypass grafting surgery

Background. Propofol can scavenge free radicals because it hasa chemical structure similar to antioxidants. Methods. We examined if free radical scavenging occurs withpropofol during CABG operations. We studied 24 patients undergoingCABG surgery for triple vessel disease, randomized into twogroups. After induction of anaesthesia with fentanyl 10 µgkg^–1 and midazolam 0.1 mg kg^–1, patients in thefentanyl group (n=14) received fentanyl infusion 10–30µg kg^–1 h^–1 and patients in the propofol group(n=10) received propofol infusion 3–6 mg kg^–1 h^–1for maintenance of anaesthesia. Atrial tissue biopsies weretaken during cannulation for bypass, 45 min after cross-clampinsertion, 5 min after unclamping, and in the decannulationperiod. Lipid peroxidation was assessed by measurement of thiobarbituricacid reactive substances (TBARS) in the atrial tissue samples. Results. Lipid peroxidation in the propofol group was less thanin the fentanyl group (P<0.05) in all sampling periods. Lipidperoxidation in the fentanyl group increased significantly duringcardiopulmonary bypass (CPB) (P<0.05), but no increase wasfound in the propofol group (P>0.05). Conclusion. In clinical doses, propofol strongly attenuateslipid peroxidation during CABG surgery. Br J Anaesth 2002; 89: 242–6     

Protective effects of cyclosporine and allopurinol on transient global cerebral ischemia in gerbils

The effects of cyclosporine and allopurinol on neuronal death following global cerebral ischemia were evaluated in Mongolian gerbils. The animals were randomly divided into four groups of 12 each: (1) sham operation as control, (2) occlusion of the bilateral common carotid arteries for 12 min and treatment with physiological saline, (3) occlusion plus treatment with 5 mg/kg of cyclosporine, and (4) occlusion plus treatment with 100 mg/kg of allopurinol 30 min before cerebral ischemia and daily thereafter for 6 days. On the 7th day after ischemia or sham operation, the gerbils' brains were removed. The number of necrotic pyramidal cells in the cortex and hippocampal CA1 was evaluated and tissue chemiluminescence (reflecting the presence of superoxide radicals) and lipid peroxides were examined. The number of necrotic pyramidal cells in each field of view (×100) of the cortex was 115±79 after ischemia, which was significantly larger than 14±8 in the control group, and was 45±33 and 60±49 after treatment with cyclosporine and allopurinol, respectively. The number of surviving pyramidal cells per mm length after ischemia in CA1 was 37±14, which was significantly smaller than 174±30 in the control group, but 78±31 following treatment with was cyclosporine, and 108±53 with allopurinol. A reduced number of necrotic pyramidal cells was associated with lower tissue chemiluminescence and lipid peroxides. The results suggest that both cyclosporine and allopurinol can inhibit neuronal death after global cerebral ischemia, and that autoimmunization and superoxide radicals are partially responsible for neuronal death.     

氯胺酮对全脑缺血大鼠的脑保护作用

目的探讨氯胺酮对全脑缺血大鼠的脑保护作用。方法健康成年SD大鼠30只,随机均分为缺血加氯胺酮组(A组)、缺血组(B组)、假手术组(C组)。以Pulsinelli-Brierley方法为标准建立四动脉阻断法全脑缺血模型,A、B组行全脑缺血15min后再灌注,其中A组于全脑缺血5min时腹腔给氯胺酮100mg/kg,B组相同时间腹腔内注射同体积生理盐水,C组分离椎动脉及颈总动脉后不行全脑缺血。再灌注3d后经心脏灌注固定后取脑制作石蜡切片,分别行HE染色观察海马CA1区神经元存活数目和TUNEL法检测海马CA1区神经元凋亡。结果C组大鼠海马CA1区神经元大部分存活,少量神经元凋亡;B组神经元很少存活,大量凋亡,细胞计数明显少于C组(P<0.01);A组神经元存活数目明显少于C组,但多于B组(P<0.01),凋亡数目明显多于C组,但少于B组(P<0.01)。结论氯胺酮对脑缺血大鼠具有一定的脑保护作用。     

The combined neuroprotective effects of lidocaine and dexmedetomidine after transient forebrain ischemia in rats

Background: We investigated whether coadministration of lidocaine and dexmedetomidine would reduce brain injury following transient forebrain ischemia in rats to a greater extent than either drug alone.
Methods: Adult male Sprague–Dawleyrats were anesthetized with halothane to maintain normocapnia and normoxia. Rats received subcutaneous injection of saline 1 ml/kg, lidocaine 10 mg/kg, dexmedetomidine 3 μg/kg, or lidocaine 10 mg/kg plus dexmedetomidine 3 μg/kg. Thirty minutes after the drug injection, forebrain ischemia was induced by hemorrhagic hypotension and occlusion of the bilateral carotid arteries, and was confirmed by isoelectric EEG. At the end of 10-min ischemia, rats were reperfused. The same dose of drugs was administered 3, 24, and 48 h after ischemia. Neurological examination was done at 1, 2, and 7 days after ischemia. Seven days after ischemia, the brain was stained with hematoxylin and eosin. We counted ischemic cells in the CA1 hippocampal region, striatum, and cerebral cortex. We also measured extracellular glutamate and norepinephrine concentration in hippocampal CA1 in the four groups.
Results: As compared with saline-treated rats, rats receiving dexmedetomidine plus lidocaine showed less than neurological deficit scores at 2 and 7 days after ischemia, and had less ischemic cells in the CA1 region. However, administration of dexmedetomidine plus lidocaine did not alter the area under the glutamate concentration curve and norepinephrine concentration during ischemia in the CA1 region, compared with saline-treated rats.
Conclusions: Our results suggest coadministration of lidocaine and dexmedetomidine improves the neurological outcome without alteration of glutamate and norepinephrine concentrations during forebrain ischemia in rats.     

亚低温对前脑缺血再灌注损伤沙土鼠海马p-ERK、p-JNK水平的影响

目的 研究亚低温对前脑缺血再灌注损伤沙土鼠海马磷酸化胞外信号调节激酶（p-ERK）及磷酸化c-Jun氨基末端蛋白激酶（p-JNK）水平的影响。方法 蒙古沙土鼠120只，随机分为4组（n=30）：常温假手术组（SH组）、常温缺血再灌注组（IR组）、低温假手术组（HSH组）、常温缺血低温再灌注组（HIR组）。腹腔注射1％戊巴比妥钠40mg／kg麻醉后，分离出双侧颈总动脉，IR组、HIR组分别夹闭双侧颈总动脉，5min后恢复脑血流灌注，IR组再灌注时维持正常体温（36．5—37．5℃），HIR组再灌注即刻开始降温，10min内降至32．5—33．5℃，并维持4h；SH组、HSH组只分离双侧颈总动脉不夹闭，SH组维持正常体温，HSH组分离双侧颈总动脉后5min开始降温，10min内降至32．5—33．5℃，并维持4h。每组于再灌注2h,4h、1d、3d、5d分别随机取6只动物，采用开阔法观察沙土鼠的行为学，行为学观察完毕立即处死大鼠，取脑组织，采用TUNEL法检测海马CA1区、CA3区细胞凋亡情况，免疫组化法测定海马CA1区、CA3区、DG区p-ERK、p-JNK的水平。结果HIR组再灌注1—5d沙土鼠行为学异常及海马凋亡细胞计数较IR组降低（P〈0．01）；与SH组或HSH组比较，IR组及HIR组再灌注期间海马CA3区及DG区p-ERK水平增加（P〈0．05），但IR组与HIR组比较差异无统计学意义；4组海马CA1区均无p-ERK表达。与sH组比较，IR组再灌注2h-5d海马CA1区、CA3区p-JNK水平增加，且HIR组再灌注2h-1d海马CA1区、CA3区p-JNK水平低于IR组（P〈0．05）。结论 亚低温（32．5-33．5℃）4h可减轻沙土鼠脑缺血再灌注损伤，其机制与抑制再灌注早期p-JNK的激活有关，而与p-ERK水平无关。     

色甘酸钠对沙土鼠前脑缺血再灌注损伤的影响

目的 探讨色甘酸钠对沙土鼠前脑缺血再灌注损伤的影响.方法 健康清洁级雄性蒙古沙土鼠24只,体重55～70 g,随机分为3组(n=8):假手术组(SH组)、缺血再灌注组(M组)及缺血再灌注+色甘酸钠组(CS组).分离双侧颈总动脉,夹闭10 min后恢复血流2 h,建立前脑缺血再灌注模型.SH组仅游离双侧颈总动脉,但不阻断脑血流;CS组于再灌注即刻和再灌注1 h时,分别经舌静脉注射色甘酸钠25 mg/kg(生理盐水稀释为25 mg/ml);M组给予等容量生理盐水.再灌注2 h时处死大鼠,取脑组织,光镜下观察病理学结果,并进行病理学评分;测定脑组织水、丙二醛(MDA)及组胺含量、超氧化物歧化酶(SOD)活性.结果 与SH组比较,M组病理学评分、脑组织水、MDA及组胺含量升高,SOD活性降低(P＜0.05或0.01);与M组比较,CS组病理学评分、脑组织水、MDA及组胺含量降低,SOD活性升高(P＜0.05或0.01).结论 色甘酸钠可减轻沙土鼠前脑缺血再灌注损伤,其机制可能与减少组胺释放和减轻氧化应激反应有关.     

Neuroprotective effect of mivazerol, an alpha 2-agonist, after transient forebrain ischemia in rats

BACKGROUND: We examined whether mivazerol, an alpha2-agonist, had neuroprotective effects after transient forebrain ischemia in rats. METHODS: Male Sprague-Dawley rats, anesthetized with halothane, were assigned to one of four groups (n=10 each): control (C, normal saline) and mivazerol 10 microg/kg (M10), 20 microg/kg (M20) and 40 microg/kg (M40) groups. Thirty minutes after drug administration, forebrain ischemia was induced with hemorrhagic hypotension and bilateral carotid artery occlusion for 10 min, and then the brain was reperfused. The neurologic outcome was evaluated 24 h, 48 h and 7 days after ischemia, followed by histologic evaluation. RESULTS: The survival rate during 7 days was significantly lower in group M40 than in groups M10 and M20 (P<0.05). The neurologic outcome was significantly better in groups M10 and M20 than in group M40 7 days after ischemia (P<0.05). The number of intact neurons in hippocampal CA1 was significantly greater in group M20 than in the other groups (P<0.05). Neuronal injury in the neocortex was significantly less in group M20 than in groups C and M40 (P<0.05). CONCLUSIONS: Our results suggest that mivazerol, up to 20 microg/kg, provides neuroprotective effects, whereas 40 microg/kg may exaggerate neuronal injury after transient forebrain ischemia in rats.     

The effects of memantine on lipid peroxidation following closed-head trauma in rats

Memantine is an uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist. Unlike other NMDA antagonists, it has been used clinically for years for the treatment of Parkinsons disease, spasticity, and dementia without serious side effects. We aimed to investigate the therapeutic efficacy of memantine on a closed head trauma model. A total of 132 adult male Sprague–Dawley rats were randomly divided into four groups: sham-operated, control (closed head trauma), sham-vehicle (closed head trauma + saline), treatment (closed head trauma + memantine, 10 mg/kg, i.p.). A cranial impact was delivered to the skull, just in front of the coronal suture, over the left hemisphere, from the height of 7 cm. Saline or memantine were applied 15 min after trauma. Rats were euthanased 0.5, 1, 2, 6, 24, 48 h after trauma. Brain tissue samples were taken 5 mm away from the left frontal pole and also from the corresponding point of the contralateral hemispheres. Malondialdehyde activity (MDA) was considered to reflect the degree of lipid peroxidation. The MDA levels continued to increase for the first 2 h after the injury, then started to decrease gradually. Memantine treatment significantly reduced lipid peroxidation levels in the treatment group compared with other groups (P<0.01). The findings of the present study indicate that memantine provides beneficial effects after closed head trauma in rats.