Global Cerebral Ischemia-reperfusion Injury Research Articles

Effects of dexmedetomidine on global cerebral ischemia-reperfusion injury in rats

Objective To investigate the effects of dexmedetomidine on global cerebral ischemia-reperfusion (I/R) injury in rats.Methods Fifty-four adult male SD rats weighing 200-250 g were randomly divided into 3 groups (n =18 each): shame operation group (group S),global cerebral I/R group (group I/R) and dexmedetomidine group (group D).Global cerebral I/R was produced by occlusion of bilateral common carotid arteries combined with hypotension (MAP maintained at 35-45 mm Hg).In group D dexmedetomidine 3 μg/kg was injected iv immediately after I/R,followed by infusion of dexmedetomidine at a rate of 3 μg· kg- 1 · h- 1 until 2 h of reperfusion.The neurological deficit score (NDS) was assessed (0 =normal,100 =brain death) at 6 h (T1),24 h (T2)and 72 h (T3) of reperfusion.Then six rats were sacrificed in each group and brain tissues were removed for microscopic examination of hippocampus CA1 region and determination of activity of myeloperoxidase (MPO),contents of TNF-α and IL-1β and expression of glial fibrillary acidic protein ( GFAP).Results Compared with group S,NDS,MPO activity and the contents of TNF-α and IL-1β at T1-3 were significantly increased,the expression of GFAP was up-regulated at T2,3 in groups I/R and D ( P ＜ 0.05 or 0.01).Compared with group I/R,NDS,MPO activity and TNF-α concent were significantly decreased at T1-3,IL-1β concent was decreased at T1,2,the expression of GFAP was down-regulated at T2,3 in group D (P ＜ 0.05 or 0.01 ).The pathologic changes were significantly attenuated in group D as compared with group I/R.Conclusion Dexmedetomidine can attenuate global cerebral I/R injury in rats,and the inhibition of inflammatory response may be involved in the mechanism. Key words: Dexmedetomidine; Reperfusion injury; Brain

Effect of tea polyphenols on global cerebral ischemia reperfusion injury in rats

Objective To investigate the effect of tea polyphenols on global cerebral ischemia reperfusion injury in rats.Method Forty-five pathogen-free male SD rats weighing 180-220 g were randomly divided into 3 groups( n =15 each):sham operation group (group S),cerebral ischemia reperfusion group (group IR) and tea polyphenols group (group TP).Global cerebral ischemia reperfusion injury was establish by four-vessel occlusion method.At 24 h of reperfusion,five rats were chosen and Evan's blue(EB) was injected iv,and then sacrificed and brain was removed for determination of EB content; another five rats were sacrificed and brain was removed for determination of water content; five rats were chosen for Morris water maze test.Result Compared with group S,EB content and water content in brain tissue were increased in groups IR and 'rP,and escape latency was prolonged,frequency of crossing the original platform was reduced in group IR ( P ＜ 0.05 ).Compared with group IR,EB content and water content in brain tissue were decreased,and escape latency was shortened,frequency of crossing the original platform was increased in group Tp ( P ＜ 0.05).Conclusion Tea polyphenols can attenuate global cerebral ischemia reperfusion injury in rats. Key words: Phenols; Tea; Reperfusion injury; Brain

Role of mitochondrial permeability transition pore of hippocampai neurons in process of hydrogen-rich saline attenuating global cerebral ischemia-reperfusion injury in rats

Objective To investigate the role of mitochondrial permeability transition pore (mPTP) of hippocampal neurons in process of hydrogen-rich saline attenuating global cerebral ischemia-reperfusion (I/R) injury in rats.Methods Seventy-two male Sprague Dawley rats,weighing 250-300 g,were randomly divided into six groups ( n =12 each):sham operation group (group S),cerebral ischemia-reperfusion group (group IR),normal saline group (group NS),hydrogen-rich saline group (group H),atractyloside group (group A) and hydrogen-rich saline + atractyloside group (group HA).Global cerebral I/R injury was produced by four-vessel occlusion method.Bilateral vertebral arteries were cauterized.Then bilateral common carotid arteries were occluded for 15min and followed by reperfusion.In groups H and HA,hydrogen-rich saline 5 ml/kg was injected intraperitoneally immediately after reperfusion,while equal volume of normal saline was injected in the other four groups.The rats in groups A and HA received intracerebroventricular injection of atractyloside 15 μl 10 min before reperfusion,while groups NS and H received intracerebroventricular injection of equal volume of normal saline.After the neurological behavior was evaluated at 24 h of reperfusion,8 rats in each group were sacrificed and the hippocampi were immediately isolated and homogenized followed by density gradient centrifugation.The opening degree of mPTP was assayed with spectrophotometry and the mitochondrial membrane potential (MMP) was detected with Rhodamine 123 method.Four rats in each group were killed at 72 h of reperfusion and the brains were removed for microscopic examination of the area CA1 of the hippocampus and determination of the number of normal pyramidal neurons.Results Compared with group S,the neurological behavior was compromised,MMP was decreased and mPTP opening degree was enhanced in the other five groups ( P ＜ 0.05).The neurological behavior was better,MMP was increased and mPTP opening degree was decreased in groups H and HA as compared with group IR ( P ＜ 0.05).Compared with group H,the neurological behavior was compromised,MMP was decreased and mPTP opening degree was enhanced in group HA ( P ＜ 0.05).Compared with group IR,the number of normal pyramidal neurons at 72 h of reperfusion in the CA1 region of the hippocampus was higher in group HA ( P ＜0.05).The injury of the CA1 region of the hippocampus at 72 h of reperfusion was attenuated in group H as compared with groups IR,NS,A and HA.Conclusion Hydrogen-rich saline can attenuate global cerebral I/R injury throngh inhibiting the mPTP opening and reducing the dissipation of MMP,thus maintaining the mitochondrial function. Key words: Hydrogen; Reperfusion injury; Brain; Mitochondrial permeability transition pore; Membrane potentials

Effects of remote ischemic-postconditioning on global cerebral ischemia-reperfusion injury in rats

Objective To investigate the effects of remote ischemic postconditioning (RIPoC) on global cerebral ischemia-reperfusion (I/R) injury in rats.Methods One hundred and twenty-eight male adult SD rats weighing 200-250 g were randomly divided into 4 groups ( n =32 each):sham operation group (group S),group I/R,group I/R + RIPoC and remote I/R group (group RI/R ).Global cerebral I/R was induced by four-vessel occlusion.Group I/R + RIPoC received 3 cycles of 15 min reperfusion followed by 15 min ischemia in bilateral femoral arteries at the beginning of cerebral reperfusion.The rats were sacrificed at 24 and 48 h of cerebral reperfusion,and brains were removed for determination of neuronal apoptosis (by TUNEL method) in hippocampal CA1 region and the parietal cortex,Bcl-2 and Bax expression (by Western blot) in hippocampal CA1 region.The superoxide dismutase (SOD) and catalase (CAT) activity and malondialdehyde (MDA) content in hippocampal CA1 region and the parietal cortex were also measured at 48 h of cerebral reperfusion.Morris water maze task was used to test the learning and memory function at 4 d of cerebral reperfusion,and the rats were sacrificed at 7 d of cerebral reperfusion,and brains were removed for determination of neuronal density in hippocampal CAl region and the parietal cortex.Results Cerebral I/R significantly increased the number of apoptotic neurons and MDA content,upregulated Bcl-2 and Bax expression,decreased neuronal density,SOD and CAT activity and learning and memory function in group I/R as compared with group S.RIPoC significantly attenuated these cerebral I/R-induced changes.Conclusion RIPoC could protect brain against global cerebral I/R-induced injury,and the mechanism may be related to inhibiting lipid peroxidation,regulating the balance between Bcl-2 and Bax and inhibiting apoptosis. Key words: Lower extremity ; Reperfusion injury; Brain; Ischemic postconditioning

Effect of thymoquinone and Nigella sativa seeds oil on lipid peroxidation level during global cerebral ischemia–reperfusion injury in rat hippocampus

Effect of thymoquinone and Nigella sativa seeds oil on lipid peroxidation level during global cerebral ischemia–reperfusion injury in rat hippocampus

Effects of hydrogen-rich saline given during reperfusion on global cerebral ischemia-reperfusion injury in rats

Objective To evaluate the effect of hydrogen-rich saline given during reperfusion on global cerebral ischeraia-reperfusion (I/R) injury in rats.Methods Seventy-two adult male SD rats,aged 2.0-2.5 months,weighing 260-300 g,were randomly divided into 3 groups (n ＝ 24 each):sham operation group (group S),group I/R and hydrogen-rich saline group (group H).In groups I/R and H cerebral I/R was induced by occlusion of 4 vessels( cauterization of bilateral carotid arteries and 15 min occlusion of bilateral common carotid arteries).In group H intraperitoneal 0.6 mmol/L hydrogen-rich saline 5 ml/kg was injected at 6 h of reperfusion,while equal volume of normal saline was injected instead of hydrogen-rich saline.Eighteen rats of each group were sacririced at 24 h of reperfusion,and then the hippocampi were removed for determination of malondialdehyde (MDA),tumor necrosis factor-α (TNF-α),interleukin-6 (IL-6)contents,and nuclear factor-κB (NF-κB) activity and activated caspase-3 expression.Another six rats of each group were sacrificed at 72 h of reperfusion,and then brain tissues were removed for microscopic examination and counting the number of uninjured pyramidal cells in hippocampal CA1 region.Results Compared with S group,the contents of MDA,TNF-α,IL-6 and NF-κB activity were significantly increased,activated caspase-3 expression was significantly up-regulated,uninjured pyramidal cells in hippocampal CA1 region were significantly decreased in I/R group( P < 0.05).Hydrogen-rich saline given during reperfusion attenuated the above-mentioned I/R-induced changes( P < 0.05 ).The histologic damage of the hippocampal CA1 region was significantly slighter in group H than group I/R.Conclusion Hydrogen-rich saline given during reperfusion can reduce global cerebral I/R injury in rats through inhibition of lipid peroxidation,inflammatory response and apoptosis. Key words: Hydrogen; Reperfusion injury; Brain

The protective effect of propofol against global cerebral ischemia/reperfusion injury in rats

Objective To investigate the protective effects of propofol on global cerebral ischemia-reperfusion injury (I/RI)in rats and the underlying mechanism. Methods 65 male Wistar rats weighting 250 g-300 g were randomly divided into 5 groups (n=13): group S sham operation, group ischemia/reperfusion (I/R), group P1 propofol (0.5 mg·kg1·min-1)+I/R, group P2 propofol (1.0 mg·kg-1·min-1)+I/R and group P3 propofol (1.5 mg·kg-1·min-1)+I/R. I/R group was induced by occlusion of bilateral common carotid arteries combined with controlled hypotension for 10 min. In group P1, P2and P3, propofol was continued intravenous infusion for 60 min before FR. The neurological behavior was evaluated at 6, 24, 48, 72 h, 4, 5, 6 d and 7 d after I/R. Rats were killed at 7 d in each group and the brains were removed for pathomorphologic examination of the survived pyramidal neurons in the area of CA1 hippocampus. Flow cytometric was applicated for detection apoptosis at 24 h of reperfusion in each group. Results The rats subjected to ischemic and reperfusion appeared behavioral defects. The behavior of animals was significantly better in group P2 and in groups P3 than that of in groups P1 and I/R. The HG scores of normal neurons in CA1 of hippocampus in S group, I/R group, P1 group, P2 group, P3 group was 0, 2.8±0.4, 2.6±0.5, 2.0±0.7, 1.4±0.5, respectively. The apoptosis rates in S group, I/R group, P1 group, P2 group, P3group was (6.5±0.6), (51.5±2.8), (48.2±0.6), (24.7±1.2), (18.6±0.8)％, respectively. Conclusion Propofol confers dose-dependent protection against cerebral I/R injury, and this effect may be involved in the anti-apoptosis effect of propofol. Key words: Ischemia/reperfusion injury; Propofol; Neurological behavior; Apoptosis

Role of acid-sensing ion channels in global cerebral ischemia-reperfusion injury in rats

Objective To investigate the role of acid-sensing ion channels (ASICs) in global cerebral ischemia-reperfusion (I/R) injury in rats. Methods Forty-eight adult male Sprague-Dawley rats weighing 250-310 g were randomly divided into 4 groups ( n = 12 each): sham operation group (group S); global cerebral I/R group (group I/R); normal saline group (group NS) and specific ASIC blocker amiloride group (group A). Global cerebral I/R was produced by occlusion of 3 vessels ( 10 min occlusion of the bilateral common carotid arteries and basilar artery) followed by reperfusion. In group NS and A, NS 6 ml/kg and amiloride 0.6 mg/kg were injected through femoral vein immediately before reperfusion respectively. Six rats in each group were selected, the dialysate in CA1 area was collected before ischemia (baseline), immediately after ischemia and during 20 min reperfusion (once every 10 min) for determination of lactate concentrations. The left 6 rats in each group were elected at 8 h of reperfusion and the open field test and inclined plane test were peeformed to assess neurological behavior.The rats were then sacrificed and brain tissues taken for microscopic examination and brain water content was calculated. Results Compared with group S, the concentration of lactate in the dialysate and brain water content were significantly increased and neurological deficits developed in group I/R and NS (P ＜ 0.05). Compared with group I/R, the concentration of lactate in the dialysate and brain water content were significantly decreased and neurological deficits were improved in group A ( P ＜ 0.05 ), but no significant change in the parameters mentioned above was found in group NS ( P ＞ 0.05). Microscopic examination showed that the damage to the brain tissues was attenuated in group A compared with group I/R. Conclusion ASICs are involved in the development of global cerebral I/R injury in rats. Key words: Ion channels; Hydrogen-ion concentration; Reperfusion injury; Brain

GW1929: A nonthiazolidinedione PPARγ agonist, ameliorates neurological damage in global cerebral ischemic-reperfusion injury through reduction in inflammation and DNA fragmentation

Transient global cerebral ischemia results in acute neurodegeneration in selective brain areas. Global cerebral ischemic-reperfusion (IR) injury induced selective hippocampal damage results into various neurobehavioral deficits including spatial memory and learning deficiencies. In this study, we have investigated the protective effects of a nonthiazolidinedione PPARγ agonist, N-(2-benzoylphenyl)-O-[2-(methyl-2-pyridinylamino)ethyl]- l-tyrosine (GW1929), against global cerebral IR injury induced neurobehavioral deficits and brain damage in gerbils. Bilateral carotid artery occlusion induced global cerebral ischemia in gerbils resulted in neurological deficits, hyperlocomotion, reduced response latency in passive avoidance test and hippocampal damage. Hippocampal neurodegeneration after cerebral IR injury was also associated with significant increase in iNOS and MMP-9 immunoreactivity along with TNFα and IL-6 levels. Massive apoptotic DNA fragmentation as evident from increased TUNEL (terminal deoxynucleotidyl transferase mediated dUTP nick end labelling)-positive cells was also observed in the CA1 hippocampal region of IR challenged gerbils. GW1929 treatment significantly ameliorated cerebral IR induced neurological symptoms, hyperlocomotion, cognitive deficits and hippocampal neuronal damage in CA1 hippocampus region in gerbils. Significant reduction in IR injury induced iNOS and MMP-9 immunoreactivity, TNFα and IL-6 levels and apoptotic DNA fragmentation was also observed with GW1929 treatment. Pioglitazone, thiazolidinedione PPARγ agonist also exhibited similar effects on inflammatory parameters after global cerebral IR injury. In summary, this study demonstrates neuroprotective effects of GW1929 in global cerebral IR injury induced neurobehavioral deficits and brain pathology which may be attributed to reduced inflammation and apoptotic DNA fragmentation, suggesting therapeutic potential of PPARγ agonists in cerebral IR injury.

Pros and cons of permissive hypercapnia in patients with subarachnoid haemorrhage and ARDS

Petridis and colleagues describe their results of intracranial pressure (ICP) analysis in 12 patients after subarachnoid haemorrhage (SAH) treated with permissive hypercapnia due to acute respiratory distress syndrome (ARDS) [6]. The study is of interest for physicians practicing neurosurgical intensive care, since many patients who suffer from severe SAH develop serious pulmonary problems during their stay in the intensive care unit. In general, these patients have a very high mortality rate and, therefore, the authors have to be congratulated on their good results. However, there are several aspects of the paper which should compel the reader to interpret the results very carefully: On the one hand, the regimen described is in contrast to the widely accepted opinion that hypercapnia should be avoided in brain-damaged patients, since hypercarbia potentially leads via acidosis-induced cerebral vasodilatation to an increase of intracranial blood volume which again leads to an increase of ICP [1–3, 5, 7]. Therefore, patients with elevated ICP have notably been excluded from studies on permissive hypercapnia [1]. Also other side effects of hypercarbia—especially severe acidosis with its deleterious effects in intensive care medicine— have to be kept in mind. On the other hand, there are animal studies demonstrating a beneficial effect of hypercapnia on the central nervous system: Zhou and colleagues concluded in their recently published paper that mild to moderate hypercapnia is neuroprotective after transient global cerebral ischemia–reperfusion injury, whereas severe hypercapnia increased brain injury [8]. Hare and colleagues hypothesized in their paper that the combined effect of increased cerebral blood flow, PaO2, and reduced pH collectively contribute to augmenting cerebral tissue oxygen tension during hypercapnia [4]. Thus, at present a generally accepted recommendation about permissive hypercapnia in brain injured patients cannot be given. In my opinion, permissive hypercapnia should to date only be administered in patients with a therapy refractory ARDS in whom advanced methods to reduce hypercarbia—e.g., jet ventilation or interventional lung assist devices—if available—have not been successful, i.e., as a form of an individual treatment attempt. A continuously performed ICP monitoring seems to be mandatory—as performed by the authors in the paper [6]. Furthermore, it has to be pointed out that there are some methodological weaknesses of the paper [6]: This is not a controlled randomized clinical study, but the report of a retrospective observation of non-consecutive patients. Another important point is that ICP measurements have been performed while the external ventricular drainage (EVD) was still open: Thus, it is unclear whether hypercapniainduced intracranial vasodilatation has not been compensated by an increase of CSF outflow via the EVD. As a conclusion, the treatment reported in the paper by Petridis and colleagues [6]—even if there are really interesting aspects, especially the potentially neuroprotective role of mild to moderate hypercapnia [8]—cannot generally be recommended until studies with a better design, especially controlled, randomized studies, have confirmed the results.

Isoflurane Preconditioning Induces Neuroprotection by Attenuating Ubiquitin-Conjugated Protein Aggregation in a Mouse Model of Transient Global Cerebral Ischemia

In this study, we sought to clarify the role of inhibiting ubiquitin-conjugated protein aggregation in the formation of a neuroprotective effect after isoflurane preconditioning using a transient global cerebral ischemia-reperfusion injury mouse model. C57BL/6 mice were randomly assigned to 3 groups (isoflurane preconditioning [IsoPC] group, control [Con] group, and sham group, n = 24 in each group). Mice in the IsoPC group and sham group were placed in a chamber and pretreated with isoflurane (1.2% isoflurane, 98% O(2), 1 hour/day) for 5 days. Mice in the Con group were placed in the same chamber but pretreated with oxygen only (98% O(2), 2% N(2), 1 hour/day) for 5 days. Twenty-four hours after the last preconditioning day, bilateral common carotid artery occlusion was performed as a model of global cerebral ischemia for 20 minutes in the IsoPC group and Con group. The total motor scores, number of viable neurons in the CA1 region of the hippocampus, and expression levels of conjugated ubiquitin or free ubiquitin were assessed by neurological assessment, immunohistochemistry, and Western blotting (at 24 and 72 hours) after reperfusion, respectively. The total motor scores in the IsoPC group were better than the Con group (P < 0.05). Morphological observations showed that the IsoPC group had better neuron structure than in the Con group. The numbers of viable neurons in the CA1 region were significantly increased by isoflurane preconditioning compared with those in the Con group (P < 0.05). The numbers of TUNEL-positive neurons in the CA1 region were significantly decreased after isoflurane preconditioning. The density of conjugated ubiquitin staining in the CA1 region of the IsoPC group was significantly lower than in the Con group (P < 0.05) and the expression of conjugated ubiquitin in the IsoPC group was lower than in the Con group (P < 0.05). Inhibition of ubiquitin-conjugated protein aggregation may have an essential role in inducing cerebral ischemic tolerance by isoflurane preconditioning in a transient global cerebral ischemia-reperfusion injury mouse model.

Dynamic change of hydrogen sulfide during global cerebral ischemia–reperfusion and its effect in rats

Hydrogen sulfide (H 2S) is a gaseous messenger and serves as an important neuromodulator in central nervous system. In the current study, we investigated the change of H 2S and cystathionine β-synthase (CBS), an H 2S-synthesizing enzyme at different time points of reperfusion following global cerebral ischemia in rats, and the effect of exogenous H 2S on global cerebral ischemia–reperfusion injury. First, we used global cerebral ischemia–reperfusion model by occlusion of bilateral common carotid arteries and vertebral arteries. Next, we measured H 2S levels in the hippocampus, cortex and plasma, the activity of H 2S-synthesizing enzymes and expression of CBS mRNA and protein in the hippocampus and cortex at 12 h, 24 h, 48 h, 72 h and 7 days of reperfusion following 15 min cerebral ischemia. Second, we pretreated rats with different doses of sodium hydrogen sulfide (NaHS), an H 2S donor and observed its effect on neuronal injury induced by 7 days of reperfusion after 15 min global cerebral ischemia. We found that when compared to sham group the amount of H 2S in the hippocampus was increased significantly at 12 h of reperfusion after cerebral ischemia, markedly decreased at 24 h, restored to the same level as that in sham group at 48 h and maintained at 72 h and 7 days. The same change tendency in the levels of H 2S was found in the cortex as described for the hippocampus. We found a similar change tendency in the activity of H 2S-synthesizing enzymes, CBS mRNA and protein expression to that in the H 2S level at different time points of reperfusion. Furthermore, while 180 μmol/kg NaHS pretreatment deteriorated the neuronal injury after global cerebral ischemia, 25 μmol/kg NaHS attenuated the neuronal injury. We suggest that a decrease of H 2S level at 24 h of reperfusion after global cerebral ischemia may be involved in neuronal injury after cerebral ischemia and lower concentration rather than higher concentration of exogenous H 2S may offer a protection against the neuronal injury induced by global cerebral ischemia–reperfusion.

Effect of hyperbaric oxygen preconditioning on expression of Nogo mRNA,Nogo-A and NgR protein in the cerebral cortex after acute global cerebral ischemia-reperfusion injury in aged rats

Objective To investigate the effect of hyperbaric oxygen preconditioning(HOP)on expression of Nogo mRNA,Nogo-A and NgR protein in the cerebral cortex after acute global cerebral ischemia-reperfusion(I/R)injury in aged rats.Methods Forty-two aged male SD rats aged 14 months weighing 480-530 g were randomly divided into 4 groups: group Ⅰ control(group C,n = 6);group Ⅱ HOP(n = 12);group Ⅲ cerebral I/R(n = 12)and group Ⅳ HOP+I/R(n = 12).Global cerebral I/R was induced by 4-vesasl occlusion method described by Pulsinelli.Bilateral vertebral arteries were permanently occluded by cauterization,aad bilateral carotid arteries were occluded for 10 min.Successful induction of cerebral ischemia was confirmed by bilateral dilated pupils unresponsive to light and EEG changes.In group Ⅱ and Ⅳ the animals received 1 h hyperbaric oxyyen at 2 absolute atmospheric pressure per day for 5 consecutive days.In group Ⅳ(HOP+I/R)global cerebral I/R was induced at 24 h after last hyperbaric oxyyen treatment.Six animals in each group were killed at24 h after I/R in each group and their brains were removed for detection of Nogo mRNA expression(by Q-PCR)and expression of Nago-A and NgR protein(by Western blot)in cerebral cortex.Cognitive function was determined at 5 days after cerebral ischemia using Morris Water Maze in the other animals.Results The learning ability and memory were significantly decreased while the expression of Nogo mRNA and Nogo-A protein was significantly increased in group Ⅲ(I/R)and Ⅳ(HOP+I/R)as compared with control group.HOP significantly ameliorated the cerebral I/R-induced decrease in learning ability and memory and increase in Nogo mRNA and Nogo-A protein expression.Conclusion Hyperbaric oxyyen preconditioning can ameliorate acute global cerebral I/R injury-induced cognitive impairment by decreasing Nogo mRNA and Nogo-A protein expression in the brain. Key words: Hyperbaric oxygenation; Ischemic preconditioning; Reperfusion injury; Brain; Aged; Nogo; Nogo-A; NgR

Effects of BDNF pretreatment against cerebral ischemia-reperfusion injury in gerbils

Objective To investigate the effects of brain-derived neurotrophic factor (BDNF) pretreatment on neuron apoptosis and the expression of Bcl-2 and Bax protein following global cerebral ischemia-reperfusion (I/R) injury in gerbils. Method Forty-eight mongolian gerbils were randomly divided into six groups in equal number (n = 8): normal control group (group C), ischemia-reperfusion group (group I/R) and four BDNF pretreatment groups according to various lengths of time from BDNF pretreatment to ischemia-reperfusion. The BDNF pretreat-ment was carried out in gerbils with lateral ventricular injection of BDNF 0.5μg 6 h, 12 h,24 h and 48 hours be-fore cerebral ischemia, and those gerbils assigned into PR6, PR12, PR24 and PR48 groups. The global cerebral is-chemia-reperfusion was induced by occlusion of bilateral common carotid arteries for 20 minutes and then the arter-ies were released for 24 hours reperfusion. The confirmation of global cerebra ischemia was evidenced by the ap-pearance of mydriasis and disappearance of light reflex and righting reflex. Twenty-four hours later, all gerbils including those of control group were sacrificed and a piece of tissue was taken from frontal cortex just behind the optic chiasma 1～4 millimeter for making paraffin sections. Neuron apoptosis was identified by using TUNEL and immunohischemistry was used to detect the expression of Bcl-2 and Bax protein in cerebral cortex. The data were analyzed by using analysis of variance. Results There were no apoptotic cells, and expression of Bcl-2 and Bax protein positive cells found in group C. Neuron apoptosis in brain cortex was detected in I/R group and BDNF pre-treatment groups. The indexes of neuron apoptosis in BDNF pretreatment groups were markedly lower than those in group I/R (P < 0.01). Compared with group I/R, the index of expression of Bcl-2 protein positive cells was in-creased significantly in BDNF pretreatment groups (P = 0.005), while the index of expression of Bax protein posi-tive cells were decreased significantly (P < 0.01 in all groups). Among 4 BDNF pretreatment group, the lowest apoptosis index and lowest of expression of Bax protein positive cells were found in PR6 and PR12 BDNF pretreat-ment groups (P = 0.0056 and 0.001, respectively). Conclusions Different time windows of BDNF pretreatment can decrease the neuron apoptosis in different degree, and protect brain against cerebral ischemia-reperfusion injury significantly. Among BDNF pretreatment time windows, pretreatment of 6 hours and 12 hours are the better ones.The mechanism of protection of BDNF pretreatment may be attributed to inducing Bcl-2 protein expressions and in-hibiting Bax protein expressions, and thereby inhibiting neuron apoptosis. Key words: Brain ischemia; Reperfusion; Brain-derived neurotrophic factor; Apoptosis; Apoptotic related-genes

Effects of NGF pretreatment on cerebral injury in gerbils

Objective To investigate the effects and underlying mechanisms of different doses of nerve growth factor(NGF) pretreatment on neuron apoptosis and the expressions of the apoptosis-related protein, Bcl-2 and Bax, in the gerbil cerebral prefrontal cortex following global cerebral ischemia-reperfusion(I/R) injury. Methods Fifty-four gerbils were randomly divided into five groups, group C: sham operation( n = 6); group I/R( n = 12), group L( n = 12): low-dose NGF+I/R, group M( n = 12): medium-dose NGF+I/R and group H ( n = 12): high-dose NGF+I/R. Groups I/R, L, M and H were further divided into 2 subgroups according to the duration of reperfusion(24 h and 72 h). The global cerebral I/R injury model was induced by bilateral carotid artery occlusion for 20 min, followed by removal of the clamps to permit reperfusion. In groups L, M and H, NGF was injected into the lateral ventricle 24 h prior to ischemia. Terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling(TUNEL) and immunohistochemical staining were performed to detect neuron apoptosis and the expressions of Bcl-2 and Bax protein in the cerebral cortex, respectively. Results In the I/R group and NGF pretreatment groups(L, M and H groups), reperfusion for 72 h caused higher percentages of both neurons exhibiting apoptosis and Bax positive cells( P < 0.01), but lower percentages of Bcl-2 positive cells compared with the corresponding 24 h reperfusion groups( P < 0.05). All NGF pretreatment groups exhibited lower percentages of neurons exhibiting apoptosis and Bax positive cells but a higher percentage of Bcl-2 positive-cells relative to the I/R group( P < 0.01). Moreover, the high-dose NGF pretreatment group had a greater decreased neuronal apoptosis and Bax protein expression and increased Bcl-2 protein expression than either the low-or medium-dose groups. Conclusion Neuron apoptosis participates in the progression of cerebral ischemia-reperfusion injury. The protective effect of NGF pretreatment against ischemia-reperfusion-induced neuron apoptosis seems to be both time- and dose-dependent. This anti-apoptosis mechanism may be associated with upregulation of Bcl- 2 protein expression and downregulation of Bax protein expression.

Neuroprotective effects of N-stearoyltyrosine on transient global cerebral ischemia in gerbils

N-stearoyltyrosine (NsTyr), a synthesized anandamide (AEA) analogue, was evaluated for the first time in the present study for the neuroprotective effect in gerbils subjected to transient global cerebral ischemia reperfusion (IR). The extent of ischemia injury was assessed behaviorally by measuring neurological functions, passive avoidance test and Morris water maze; and histopathologically by evaluating hippocampal CA1 pyramidal damage. In addition, ischemia-induced apoptosis was examined using the terminal deoxynucleotidyl transferase-mediated UTP nick end labeling (TUNEL) method. Furthermore, in order to understand the mechanism of NsTyr's neuroprotective effect, we examined antioxidative enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), and non-enzymatic scavenger glutathione (GSH) and measured the levels of malondialdehyde (MDA) in hippocampus. The administration of NsTyr led to attenuation of ischemia-induced neural deficits both behaviorally and histopathologically, reduced the level of MDA, significantly increased the activity of antioxidants GSH and GSH-PX, and obviously elevated the activities of SOD and CAT. Our results suggest that NsTyr shows neuroprotective effect on global cerebral IR injury and its neuroprotective effects may be attributed to restraining DNA fragmentation, suppressing the production of free radicals and elevating antioxidant capacity.

Effects of lidocaine combined ketamine on apoptosis in hippocampus following global cerebral ischemic-reperfusion injury in rats

Objective To investigate the effect of lidocaine combined ketamine to the cells necrosis and apoptosis in the CA1 region of rat hippoeampus following global cerebral ischemia-reperfusion. Methods Sixty adult Wistar rats were randomly divided into 6 groups:control group(Ⅰ, n=4),sham operation group (Ⅱ, n=4), model group (Ⅲ, n =4), lidoeaine group (Ⅳ, n =16), ke-tamine group(Ⅴ, n=16), lidocaine and ketamine group (Ⅵ, n=16). The global cerebral ischemia (10 min) was induced by the use of the four-vessel occlusion method. Group Ⅳ,Ⅴ,Ⅵ intraperitoneally injected the lidocaine 10mg/kg, ketamine 10 mg/kg or lidocaine combined ketamine 10 mg/kg. The effect of cells necrosis and apoptosis was detected by using HE staining and TUNEL methods. Results Compared with group Ⅱ the numbers of ischemia neuron of group Ⅳ, Ⅴ, Ⅵ had significant deviation (P<0.05) in 24 h, and group Wl had significant decreased than group Ⅳ, Ⅴ(P<0.05). The isehemia neurons peak presented in 24 h. Compared with group Ⅱ the numbers of apoptosis of group Ⅳ,Ⅴ,Ⅵ had significantly deviation (P<0.05)in 24 h, and group Ⅵ had significantly decreased than group Ⅳ,Ⅴ (P<0.05). The apoptosis peak presented in 24 h and 48 h, and decreased during reperfusion time. Conclusion Li-doeaine combined ketamine can reduce the cell necrosis and apoptosis after global erebral isehemia-reperfusion in rats hippocampus. Key words: Lidocaine; Ketamine; Ischemic-reperfusion; Hippocampus; Apoptosis

Effects of salidroside-pretreatment on neuroethology of rats after global cerebral ischemia-reperfusion

To study the effects of salidroside-pretreatment on changes of neuroethology in rats with global cerebral ischemia-reperfusion injury so as to investigate its probable mechanism. Sixty SD male rats were randomly divided into sham-operated group, untreated group and salidroside-pretreated group. The rats in salidroside-pretreated group were intraperitoneally administered with salidroside for seven days. The dose of salidroside was 12 mg/(kg.d). Thirty minutes after the last administration, the acute global cerebral ischemia-reperfusion in rats of the untreated group and the salidroside-pretreated group was induced by using the modified Pulsinelli's 4-vessel occlusion method. Five rats in each group were killed to obtain their brains 24 hours after reperfusion. The water content in the right brain was measured by calculating the ratio of dry weight to wet weight of the right brain. Activity of superoxide dismutase (SOD) and content of malondialdehyde (MDA) in hippocampus of the rats were measured. Then neurological severity scores (NSSs) of the other 15 rats in each group were observed respectively before and 6, 12, 24, 48 and 96 h after reperfusion. At the fifth day after reperfusion, the test of Morris water maze was carried out to examine the memories and learning abilities of the rats. The content of MDA, the activity of SOD, the NSS, the mean incubation period and the ratio of time in the second quadrant in the untreated group were significant different from those in the sham-operated group (P<0.05). Compared with the untreated group, the brain water content, the content of MDA and the NSS degraded, and the mean incubation period shortened in salidroside-pretreated group. The activity of SOD and the ratio of residence time in the second quadrant increased in salidroside-pretreated group as compared with the untreated group (P<0.05). Salidroside can reduce the degree of cerebral edema of rats with global cerebral ischemia-reperfusion injury, relieve the metabolism abnormity of free radical and improve the function of cognition.

Protective effects and mechanism of puerarin on learning-memory disorder after global cerebral ischemia-reperfusion injury in rats

To observe the effect of puerarin on the learning-memory disorder after global cerebral ischemia-reperfusion injury in rats, and to explore its mechanism of action. The global cerebral ischemia-reperfusion injury model was established using the modifified Pulsinelli four-vessel occlusion in Sprague-Dawley rats. Rats were intraperitoneally injected with puerarin (100 mg/kg) 1 h before ischemia and once every 6 h afterwards. The learning-memory ability was evaluated by the passive avoidance test. The dynamic changes of the cell counts of apoptosis and positive expression of Bcl-2 in the hippocampus CA1 region were determined by the TUNEL and immunohistochemical methods, respectively. (1) Compared with the reperfusion group, the step through latency (STL) in the passive avoidance test in the puerarin group was prolonged signifificantly (P<0.01). (2) The apoptotic neurons were injured most severely on the 3rd day in the hippocampal CA1 region after global ischemia and reperfusion. In the puerarin group, the number of apoptotic cells decreased at respective time points after ischemia-reperfusion (P<0.01). (3) The level of positive expression of Bcl-2 varied according to the duration of reperfusion and the peak level occurred on day 1 in the hippocampal CA1 region after global cerebral ischemia. Compared with the reperfusion group, the expression of Bcl-2 in the puerarin group was up-regulated at the respective time points after ischemia reperfusion (P<0.01), reaching the peak on day 1. Puerarin could improve the learning-memory ability after global cerebral ischemia and reperfusion in rats. The protective mechanism might be related to the effect of inhibiting or delaying the cell apoptosis through up-regulating the expression of Bcl-2 after ischemia and reperfusion.

Protective Effects of Pioglitazone Against Global Cerebral Ischemic-Reperfusion Injury in Gerbils

Despite of the huge socio-economic burden, stroke still represents an unmet therapeutic need. Researchers failed to reproduce preclinical efficacy in subsequent clinical development. To bridge this translation failure, the Stroke Therapy Academic Industry Round Table (STAIR) has suggested a rigorous, robust, and detailed preclinical evaluation in at least 2 species and multiple cerebral ischemia models to avoid the clinical failure. Considering these recommendations, in the present study, we have investigated the effects of pioglitazone in global model cerebral ischemic-reperfusion (IR) injury in gerbils. Global cerebral IR injury, produced by bilateral carotid artery occlusion for 5 min, was characterized by neurological deficits, hyperlocomotion, and neurodegeneration in the hippocampal CA1 region. Global ischemia was also associated with oxidative stress and DNA fragmentation as evident from increased malondialdehyde (MDA) levels and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling)-positive cells. Global cerebral IR injury associated neurological damage was significantly attenuated by pioglitazone pretreatment as evident from reduction in neurological symptoms, hyperlocomotion, and CA1 hippocampal neuronal damage in IR-challenged gerbils. Pioglitazone pretreatment also attenuated the oxidative stress and DNA fragmentation after cerebral IR injury. Pioglitazone post-treatment has also significantly reduced the CA1 hippocampal neuronal damage and DNA fragmentation after cerebral IR injury in IR-challenged gerbils. This study demonstrates the neuroprotective activity of pioglitazone in global cerebral IR injury and its neuroprotective effects may be attributed to reduction in oxidative stress and DNA fragmentation.