Hypoxic-ischemic insult decreases glutamate uptake by hippocampal slices from neonatal rats: prevention by guanosine

Brain injury secondary to hypoxic-ischemic disease is the predominant form of damage encountered in the perinatal period. The impact of neonatal hypoxia-ischemia (HI) in 7-day-old pups on the high-affinity [3H] glutamate uptake into hippocampal slices at different times after insult was examined. Immediately following, and 1 day after the insult there was no effect. But at 3 to 5 days after the HI insult, glutamate uptake into the hippocampus was markedly reduced; however, after 30 or 60 days the glutamate uptake into hippocampal slices returned to control levels. Also, this study demonstrated the effect of the nucleoside guanosine (Guo) on the [3H] glutamate uptake in neonatal HI injury, maintaining the [3H] glutamate uptake at control levels when injected before and after insult HI. We conclude that neonatal HI influences glutamate uptake a few days following insult, and that guanosine prevents this action.     

Intranasal administration of IGF-1 attenuates hypoxic-ischemic brain injury in neonatal rats

To determine whether intranasal administration (iN) of recombinant human insulin-like growth factor-1 (rhIGF-1) provides neuroprotection to the neonatal rat brain following cerebral hypoxia-ischemia (HI), two doses of rhIGF-1 (50 μg at a 1 h interval) were infused into the right naris of postnatal day 7 (P7) rat pups with or without a prior HI insult (right common carotid artery ligation, followed by an exposure to 8% oxygen for 2 h). Our result showed that rhIGF-1 administered via iN was successfully delivered into the brain 30 min after the second dose. In the following studies rhIGF-1 was administered to P7 rat pups at 0, 1 or 2 h after HI at the dose described above. Pups in the control group received cerebral HI and vehicle treatment. Pups that underwent sham operation and vehicle treatment served as the sham group. Brain pathological changes were evaluated 2 and 15 days after HI. Our results showed that rhIGF-1 treatment up to 1 h after cerebral HI effectively reduced brain injury as compared to that in the vehicle-treated rats. Moreover, rhIGF-1 treatment improved neurobehavioral performance (tested on P5–P21) in juvenile rats subjected to HI. Our results further showed that rhIGF-1 inhibited apoptotic cell death, possibly through activating the Akt signal transduction pathway. rhIGF-1 enhanced proliferation of neuronal and oligodendroglial progenitors after cerebral HI as well. These data suggest that iN administration of IGF-1 has the potential to be used for clinical treatment.     

Early biochemical effects after unilateral hypoxia–ischemia in the immature rat brain

Perinatal hypoxia–ischemia (HI) gives rise to inadequate substrate supply to the brain tissue, resulting in damage to neural cells. Previous studies at different time points of development, and with different animal species, suggest that the HI insult causes oxidative damage and changes Na⁺, K⁺–ATPase activity, which is known to be very susceptible to free radical-related lipid peroxidation. The aim of the present study was to establish the onset of the oxidative damage response in neonatal Wistar rats subjected to brain HI, evaluating parameters of oxidative stress, namely nitric oxide production, lipoperoxidation by thiobarbituric acid reactive substances (TBA-RS) production and malondialdehyde (MDA) levels, reactive species production by DCFH oxidation, antioxidant enzymatic activities of catalase, glutathione peroxidase, superoxide dismutase as well as Na⁺, K⁺–ATPase activity in hippocampus and cerebral cortex. Rat pups were subjected to right common carotid ligation followed by exposure to a hypoxic atmosphere (8% oxygen and 92% nitrogen) for 90 min. Animals were sacrificed by decapitation 0, 1 and 2 h after HI and both hippocampus and cerebral cortex from the right hemisphere (ipsilateral to the carotid occlusion) were dissected out for further experimentation. Results show an early decrease of Na⁺, K⁺–ATPase activity (at 0 and 1 h), as well as a late increase in MDA levels (2 h) and superoxide dismutase activity (1 and 2 h after HI) in the hippocampus. There was a late increase in both MDA levels and DCFH oxidation (1 and 2 h) and an increase in superoxide dismutase activity (2 h after HI) in cortex; however Na⁺, K⁺–ATPase activity remained unchanged. We suggest that neonatal HI induces oxidative damage to both hippocampus and cortex, in addition to a decrease in Na⁺, K⁺–ATPase activity in hippocampus early after the insult. These events might contribute to the later morphological damage in the brain and indicate that it would be essential to pursue neuroprotective strategies, aimed to counteract oxidative stress, as early as possible after the HI insult.     

Relationship between prolonged neural suppression and cerebral hemodynamic dysfunction during hypothermia in asphyxiated piglets

Objectives

Hypothermia (HT) improves the outcome of neonatal hypoxic-ischemic encephalopathy. Here, we investigated changes during HT in cortical electrical activity using amplitude-integrated electroencephalography (aEEG) and in cerebral blood volume (CBV) and cerebral hemoglobin oxygen saturation using near-infrared time-resolved spectroscopy (TRS) and compared the results with those obtained during normothermia (NT) after a hypoxic-ischemic (HI) insult in a piglet model of asphyxia. We previously reported that a greater increase in CBV can indicate greater pressure-passive cerebral perfusion due to more severe brain injury and correlates with prolonged neural suppression during NT. We hypothesized that when energy metabolism is suppressed during HT, the cerebral hemodynamics of brains with severe injury would be suppressed to a greater extent, resulting in a greater decrease in CBV during HT that would correlate with prolonged neural suppression after insult.

Cell death in primary cultures of mouse neurons and astrocytes during exposure to and ‘recovery’ from hypoxia, substrate deprivation and simulated ischemia

Effects of hypoxia, substrate deprivationand simulated ischemia (combined hypoxia and substrate deprivation) on cell survival during the insult itself and during a 24 h ‘recovery’ period were studied in primary cultures of mouse astrocytes and in cerebral cortical neuronal-astrocytic co-cultures. Cell death was determined by release of the cytosolic high molecular enzyme lactate dehydrogenase (LDH) as well as morphologically (retention of staining with rhodamine 123 and lack of staining with propidium iodide as an indicator of live cells). Glutamate concentrations were measured in the incubation media at the end of the metabolic insults. Astrocytes were very resistant to hypoxia, but less so to simulated ischemia; under both conditions the glutamate concentrations in the media remained low. Cerebral cortical neurons were almost equally susceptible to damage by hypoxia and by stimulated ischemia, although hypoxia had a faster deleterious effects on some of the neurons and simulated ischemia during a long-term insult (9 h) killed all neurons, whereas a non-negligible neuronal subpopulation survived 9 h of hypoxia. Neuronal cell death after long-term hypoxia (but not after simulated ischemia) was correlated with high concentrations of glutamate in the incubation media. After certain insults, most notably relatively short lasting simulated ischemia (3 h) in neurons (which caused no increased cell death during the insult), there was a large release of LDH during the ‘recovery’ period.     

Relationship between early changes in cerebral blood volume and electrocortical activity after hypoxic–ischemic insult in newborn piglets

Background: Early changes in cerebral hemodynamics and depressed electrocortical activity have been reported after a hypoxic–ischemic (HI) insult. However, the relationship between these two parameters is unclear. This study aimed to examine the relationship between changes in cerebral blood volume (CBV) and cerebral Hb oxygen saturation (ScO₂) after a HI insult and the low amplitude-integrated electroencephalography (aEEG) duration concomitantly observed. Methods: Sixteen newborn piglets obtained within 24 h of birth were used (n = 3 controls). Thirteen piglets were subjected to a HI insult of 20-min low-amplitude aEEG (<5 μV, LAEEG), after which a low mean arterial blood pressure (<70% of baseline) was maintained for 10 min. We measured changes in CBV and ScO₂ using near-infrared time-resolved spectroscopy (TRS) and cerebral electrocortical activities using aEEG until 6 h after the insult. Results: A positive correlation was observed between the LAEEG duration and CBV increase, but not ScO₂, after the insult. Conclusion: These results suggest that a larger increase in CBV reflected a more severe failure in cerebral circulation to maintain cell membrane action potentials, which induced a more extended recovery period of electrocortical activity after the insult. We conclude that an early increase in CBV and longer LAEEG indicate severe brain injury.     

Alcohol consumption increases basal extracellular glutamate in the nucleus accumbens core of Sprague–Dawley rats without increasing spontaneous glutamate release

Glutamate neurotransmission in the nucleus accumbens core (NAc) mediates ethanol consumption. Previous studies using non‐contingent and voluntary alcohol administration in inbred rodents have reported increased basal extracellular glutamate levels in the NAc. Here, we assessed basal glutamate levels in the NAc following intermittent alcohol consumption in male Sprague‐Dawley rats that had access to ethanol for 7 weeks on alternating days. We found increased basal NAc glutamate at 24 h withdrawal from ethanol and thus sought to identify the source of this glutamate. To do so, we employed a combination of microdialysis, slice electrophysiology and western blotting. Reverse dialysis of the voltage‐gated sodium channel blocker tetrodotoxin did not affect glutamate levels in either group. Electrophysiological recordings in slices made after 24 h withdrawal revealed a decrease in spontaneous excitatory postsynaptic current (sEPSC) frequency relative to controls, with no change in sEPSC amplitude. No change in metabotropic glutamate receptor 2/3 (mGlu2/3) function was detected as bath application of the mGlu2/3 agonist LY379268 decreased spontaneous and miniature EPSC frequency in slices from both control and ethanol‐consuming rats. The increase in basal glutamate was not associated with changes in the surface expression of GLT‐1, however, a decrease in slope of the no‐net‐flux dialysis function was observed following ethanol consumption, indicating a potential decrease in glutamate reuptake. Taken together, these findings indicate that the increase in basal extracellular glutamate occurring after chronic ethanol consumption is not mediated by an increase in action potential‐dependent glutamate release or a failure of mGlu2/3 autoreceptors to regulate such release.     

NOS活性在局灶脑缺血后的时相变化

一氧化氮(NO)在脑缺血中起重要作用,一氧化氮合成酶(NOS)作为NO合成的关键酶,其活性变化直接调节NO的生成量及生物学效应,本文在建立兔MCAO局灶脑缺血模型基础上,测定缺血不同时间缺血区和正常脑组织的NOS活性。结果显示脑缺血早期(1小时内)NOS活性突然升高,随之下降;脑缺血后24小时NOS活性又回升,48小时、96小时明显升高。     

局灶脑缺血后早,晚期一氧化氮合成酶的活性变化

一氧化氮(NO)在脑缺血中起重要作用,一氧化氮合成酶(NOS)作为NO合成的关键酶,其活性变化直接调节NO的生成量及生物学效应。本文在建立兔MCAO局灶脑缺血模型基础上,测定缺血后不同时间缺血区和正常脑组织的NOS活性。结果显示,脑缺血早期(1h内)NOS活性突然升高,随之下降;脑缺血后24h NOS活性又升高,至48h、96h明显升高。     

Ischemia independent lesion evolution during focal stroke in rats

Lesion evolution during focal cerebral ischemia may depend on flow restrictions or on accumulation of toxic mediators within the infarct and expansion of these factors to the periinfarct region. So far, the precise contribution of flow dependent versus spreading-mediated impairment of viable periinfarct tissue has not been determined. Therefore, we measured lesion expansion, flow restrictions and glutamate distribution on serial brain sections at different time points after experimental focal ischemia.Permanent focal ischemia was induced by occlusion of the right middle cerebral artery in male rats and the flow reduction was subsequently measured at 1, 12 and 24 h using iodo[¹⁴C]antipyrine autoradiography. Additionally, the necrotic volume was determined on serial brain sections and the glutamate content was measured in tissue samples from adjacent microdissections.Twelve hours after focal ischemia no noteworthy viable areas with blood flow restrictions of 20-40 ml 100 g^− 1 min^− 1 existed but at 24 h the necrotic tissue exceeded the hemodynamically compromised region by 40 ± 21 mm³ (24%). Furthermore, at 12 and 24 h the glutamate content was elevated in areas surrounding the infarct.Relevant flow restrictions are detectable only during early stages of infarct maturation, whereas the propagation of secondary factors may be the predominant mechanism for delayed infarct evolution.     

Wide therapeutic time window for nimesulide neuroprotection in a model of transient focal cerebral ischemia in the rat

Results from several studies indicate that cyclooxygenase-2 (COX-2) is involved in ischemic brain injury. The purpose of this study was to evaluate the neuroprotective effects of the selective COX-2 inhibitor nimesulide on cerebral infarction and neurological deficits in a standardized model of transient focal cerebral ischemia in rats. Three doses of nimesulide (3, 6 and 12 mg/kg; i.p.) or vehicle were administered immediately after stroke and additional doses were given at 6, 12, 24, 36 and 48 h after ischemia. In other set of experiments, the effect of nimesulide was studied in a situation in which its first administration was delayed for 3-24 h after ischemia. Total, cortical and subcortical infarct volumes and functional outcome (assessed by neurological deficit score and rotarod performance) were determined 3 days after ischemia. The effect of nimesulide on prostaglandin E(2) (PGE(2)) levels in the injured brain was also investigated. Nimesulide dose-dependently reduced infarct volume and improved functional recovery when compared to vehicle. Of interest is the finding that neuroprotection conferred by nimesulide (reduction of infarct size and neurological deficits and improvement of rotarod performance) was also observed when treatment was delayed until 24 h after ischemia. Further, administration of nimesulide in a delayed treatment paradigm completely abolished PGE(2) accumulation in the postischemic brain, suggesting that COX-2 inhibition is a promising therapeutic strategy for cerebral ischemia to target the late-occurring inflammatory events which amplify initial damage.     

头孢曲松钠对大鼠脑缺血损伤的保护作用及其机制

目的 探讨在大鼠局灶性脑缺血模型中应用头孢曲松钠对脑缺血损伤的保护作用及其相关机制.方法 制备Wistar大鼠局灶性脑缺血模型,并按随机数字表法分为单纯缺血组(MCAO组)、头孢曲松钠治疗组(MCAO+CTX组)和盐水对照组,其中MCAO+CTX组为缺血90min时给予头孢曲松钠200 mg/kg.缺血后24 h、48 h、7 d时对各组大鼠进行神经行为学评分和脑水肿程度测定,同时比较各组大鼠皮层和海马谷氨酸转运体功能的差异.结果 随着缺血时间延长,各组大鼠神经行为学评分逐渐提高;脑水肿在缺血后24 h、48 h时逐渐加重,至7 d时已逐渐消退.与MCAO组比较,各时间点MCAO+CTX组大鼠神经行为学评分明显提高,脑水肿程度明显减轻,伤侧皮层及海马谷氨酸转运体功能明显增强,差异均有统计学意义(P＜0.05).结论 头孢曲松钠对大鼠局灶性脑缺血损伤具有保护作用,其机制可能与增强谷氨酸转运体功能从而减轻谷氨酸神经毒性作用有关.

Abstract：

Objective To explore the neuroprotective effect of ceftriaxone on cerebral ischemia injury in rats with focal cerebral ischemia and its possible mechanism. Methods Focal cerebral ischemic models were established in Wistar rats and randomly divided into ischemic group (performed middle cerebral artery occlusion [MCAO]), ceftriaxone (CTX) therapy group (given CTX at a dosage of 200 mg/kg 90 min after MCAO) and control group (given physiological saline only). Twenty-four and 48 h, and 7 d after MCAO, neurological behaviors and cerebral edema level were evaluated in these 3 groups;glutamate transporter function in the cortex and hippocampus of rats was compared between each 2 groups. Results With time extended, neurological behaviors scores were obviously elevated in every group;and cerebral edema became worse at 24 and 48 h and decreased 7 d after MCAO. As compared with that in the ischemic group, glutamate transporter function, level of edema and neurological behaviors scores in cortex and hippocampus of rats in the CTX therapy group were statistically increased at different ischemic time points (P<0.05). Conclusion Ceftriaxone has a neuroprotective effect against focal cerebral ischemia in rats, which may relate to increased glutamate transporter function and reduced glutamate neurotoxicity.     

The influence of MK-801 on the hippocampal free arachidonic acid level and Na+,K+-ATPase activity in global cerebral ischemia-exposed rats

The influence of 20 min global cerebral ischemia on the free arachidonic acid (FAA) level and Na⁺,K⁺-ATPase activity in the rat hippocampus at different time points after ischemia was examined. In addition, the effect of MK-801 on mentioned parameters was studied. Animals were exposed to 20 min global cerebral ischemia and were sacrificed immediately, 0.5, 1, 2, 6, 24, 48, 72, and 168 h after ischemic procedure. The level of the FAA and the Na⁺,K⁺-ATPase activity was measured during all reperfusion periods examined. Various doses of MK-801 (0.3, 1.0, 3.0, and 5.0 mg/kg) had been injected 30 min before ischemic procedure started. It was found that 20 min global cerebral ischemia induces a statistically significant increase of the FAA level immediately after ischemia and during the first 0.5 h of reperfusion. After a transient decrease, the level of FAA level increased again after 24 and 168 h of recirculation. Treatment with 3.0 mg/kg of MK-801 significantly prevented the FAA accumulation immediately and 0.5 h after ischemic insult while application of 5.0 mg/kg of MK-801 exerted a protective effect during the first 24 h. Global cerebral ischemia induces the significant decline in the Na⁺,K⁺-ATPase activity in the hippocampus starting from 1 to 168 h of reperfusion. Maximal inhibition was obtained 24 h after the ischemic damage. Application of 3.0 mg/kg of MK-801 exerted statistically significant protection during the first 24 h while the treatment with 5.0 mg/kg of MK-801 prevented fall in enzymatic activity during all reperfusion periods examined. Our results suggest that, in spite of different and complex pathophysiological mechanisms involved in the increase of FAA level and the decrease of the Na⁺,K⁺-ATPase activity, blockade of NMDA receptor subtype provides a very important strategy for the treatment of the postischemic excitotoxicity.     

Optogenetic translocation of protons out of penumbral neurons is protective in a rodent model of focal cerebral ischemia

BackgroundIntracellular acidosis in the ischemic penumbra can contribute to further cell death, effectively enlarging the infarct core. Restoring the acid-base balance may enhance tissue survivability after cerebral ischemia.ObjectiveThis study investigated whether translocating protons out of penumbral neurons could mitigate tissue acidification and induce neuroprotection in a rodent model of acute cerebral ischemia.MethodsWe modulated the penumbral neurons via a light-driven pump to translocate protons out (i.e., archaerhodopsin/ArchT group) or into (i.e., channelrhodopsin-2/ChR2 group) neurons after focal cerebral ischemia in rats. Intracellular pH values were imaged via neutral red (NR) fluorescence and cerebral blood flow (CBF) was monitored through laser speckle contrast imaging (LSCI). Global CBF responses to electrical stimulation of the hindlimbs were obtained 24 h and 48 h after ischemia to assess neurological function. Behavioral and histological outcomes were evaluated 48 h after ischemia. A control group without gene modification was included.ResultsThe reduction of relative pH (R_pH), the amplitude of negative peak of hypoemic response (R_NP) and the hemispheric lateralization index (LI) in ArchT group were significantly less than those of the ChR2 or control group. Moreover, R_pH was strongly correlated with R_NP (r = 0.60) and LI (r_24h = 0.80, r_48h = 0.59). In addition, behavioral and histological results supported a neuroprotective effect of countering neuronal acidosis in penumbra through optogenetic stimulation.Conclusion(s)These results indicate that countering intracellular acidosis by optogenetically translocating protons out of penumbral neurons during the acute ischemic stage could induce protection after ischemic brain injury.     

Post-ischemic hypothermia for 24 h in P7 rats rescues hippocampal neuron: Association with decreased astrocyte activation and inflammatory cytokine expression

Hypothermia is an effective method for reducing the neuronal damage induced by hypoxia–ischemia (HI) but the underlying mechanism remains unclear. To investigate the effects of post-HI hypothermia on the developing brain, 7-day-old rats were subjected to left carotid artery ligation followed by 8% oxygen for 2 h. They were divided into a hypothermia group (rectal temperature 32–33 °C for 24 h) and a normothermia group (36–37 °C for 24 h) immediately after hypoxia–ischemia. Animals were sacrificed at 12, 24 and 72 h for gene analysis and 0, 1, 3 and 7 days for protein analysis after HI. There was a significant decrease in infarct volume in the hypothermia group at 7 days after HI compared with that in the normothermia group. The hypothermia group had more neuronal nuclei (NeuN) positive neurons and lower levels of glial fibrillary acidic protein (GFAP) mRNA and immunoreactivity in the hippocampus CA1 region than the normothermia group. Real-time PCR showed no significant difference in glial cell line-derived neurotrophic factor (GDNF) mRNA expression in the hippocampus in the two groups at various time points after HI. However, GDNF protein level was significantly increased in the hypothermia group. On the other hand, mRNA and protein levels of the inflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) were dramatically decreased in the hypothermia compared with the normothermia group. The present findings highlight an apparent association between inhibition of hippocampal neuron loss by hypothermia and decreased astrocytosis and inflammatory cytokine release after hypoxia–ischemia in the developing brain.     

Upregulation of neuronal nitric oxide synthase and mRNA, and selective sparing of nitric oxide synthase-containing neurons after local cerebral ischemia in rat

Nitric oxide synthase-containing neurons are presumed to be resistant to neurodegeneration and neurotoxicity, however this resistance has not been demonstrated after focal cerebral ischemia. We therefore measured the temporal profile of neuronal nitric oxide synthase (NOS-I) mRNA and immunoreactivity and NADPH-diaphorase reactivity over a one week period after permanent middle cerebral artery (MCA) occlusion in 48 male Wistar rats and compared these data to ischemic cell damage as evaluated on hematoxylin and eosin (H & E) stained sections by light microscopy. NOS-I mRNA increased as early as 15 min after MCA occlusion in the ipsilateral striatum and maximal expression of NOS-I was found in the ipsilateral cortex and striatum 1 h after MCA occlusion. The numbers of NOS-I-containing neurons in the ipsilateral cortex and striatum were significantly greater (P < 0.05) than NOS-I-containing neurons in the contralateral hemisphere at 2–48 h after the onset of ischemia. The number of NOS-I-containing neurons peaked at 4 h after MCA occlusion. Neurons exhibited shrinkage or were swollen at 1 to 4 h after MCA occlusion. At 24–48 h after ischemia, neurons in the ischemia lesion appeared to be eosinophilic or ghost like on H & E stained sections. However, some of these neurons retained morphological integrity on the NOS-I immunohistochemical sections. At 168 h after ischemia, all neurons within the lesion appeared necrotic on H & E stained sections; however, scatterred neurons expressed NOS-I and NADPH-diaphorase. The rapid upregulation of NOS-I and mRNA in the ischemic lesion suggests that NOS-I is involved in focal cerebral ischemic injury; the expression of NOS-I by neurons that retain their morphological structure in the area of the infarct suggests that NOS-I-containing neurons are more resistant to the ischemic insult. Our data also indicate a close association of NOS-I immunoreactivity and NADPH-diaphorase reactivity in ischemic brain.     

Electrophysiological recordings from rat hippocampus slices following in vivo brain ischemia

Pyramidal neurons in area CA1 of the septal hippocampus degenerate 2-3 days after an episode of transient global cerebral ischemia. The purpose of this study was to investigate synaptic transmission and passive neuronal properties in the post-ischemic period prior to neuronal death. Electrophysiological recordings were made from area CA1 in hippocampal slices prepared from rats which had survived a period of 20 min of ischemia for up to 5 days. In septal slices, field responses were in area CA1 unaltered up to 24 h after the ischemic insult. Forty-eight hours after ischemia, the mean amplitude of the population spike, but not the field-EPSP, was significantly reduced. In septal slices prepared more than 48 h after ischemia field potentials were absent or strongly attenuated, whereas they were intact in slices prepared from the temporal pole. No spontaneous discharges were detected in slices prepared at any time from post-ischemic rats. Intracellular recordings were obtained from slices up to 48 h after the ischemic episode. There was no significant difference in the resting membrane potential or input resistance between these neurons and those from control slices. Action potentials followed by a fast afterhyperpolarization and spike accommodation were preserved in all post-ischemic neurons. In all neurons investigated, orthodromic stimulation evoked an EPSP followed by a fast- and then a slow-IPSP. One hour after ischemia, the slow-IPSP was reduced. Forty-eight hours after ischemia, the fast-IPSP was significantly increased. The EPSP was markedly attenuated by the non N-methyl-D-aspartate receptor blocker 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM). The residual depolarizing component was amplified by perfusing with Mg(2+)-free medium and blocked by the N-methyl-D-aspartate receptor antagonist DL-2-amino-5-phosphonovaleric acid. Paired-pulse facilitation of the EPSP was also preserved. As in control slices, the slow-IPSP and paired-pulse depression of the fast-IPSP were blocked by 1 microM baclofen. The present experiments provide no evidence that overt alteration of excitatory synaptic transmission or neuronal properties favouring hyperexcitability precede the ischemically induced death of CA1 pyramidal cells.     

Electro-acupuncture preconditioning abrogates the elevation of c-Fos and c-Jun expression in neonatal hypoxic-ischemic rat brains induced by glibenclamide, an ATP-sensitive potassium channel blocker

This study aimed to clarify the neuroprotective mechanism of electro-acupuncture (EA) preconditioning on hypoxic-ischemic brain injury (HIBI). Using Western blot, the expression of c-fos protein (c-Fos) and c-jun protein (c-Jun) induced by glibenclamide, an ATP-sensitive potassium (K_ATP) channel blocker was examined from cerebral cortical and hippocampal samples in neonatal hypoxic-ischemic rats, with or without EA preconditioning. EA was performed on Hegu (LI4), a well-known acupoint commonly used in Oriental medicine for the treatment of neuronal injury resulting from hypoxia–ischemia (HI). Preconditioned rats were treated with either diazoxide, a K_ATP channel opener, glibenclamide, or sterile saline injected into the left lateral ventricle (i.c.v.), with or without EA administration before HI insult. Interestingly, low c-Fos and c-Jun expressions were found both in diazoxide and EA groups, 24 h after HI. Furthermore, significant differences in relative optical density (ROD) were found between glibenclamide and HI control groups (P≤0.05), as well as between the group administered glibenclamide after EA and the HI control group (P≤0.05). However, the level of c-Fos and c-Jun expression in the group administered glibenclamide after EA was significantly lower than in the glibenclamide group (P≤0.05). The present findings indicate that the effectiveness of EA preconditioning against HIBI may be mediated via the opening of K_ATP channels.     

Effects of the hyperbaric oxygen treatment on the Na+,K+ -ATPase and superoxide dismutase activities in the optic nerves of global cerebral ischemia-exposed rats

The effects of hyperbaric oxygen (HBO) treatment on the Na+,K+ -ATPase and superoxide dismutase (SOD) activities were examined in the optic nerves of the rats exposed to global cerebral ischemia. Animals were exposed to global cerebral ischemia of 20-min duration and were either sacrificed or exposed to the first HBO treatment immediately, 0.5, 1, 2, 6, 24, 48, 72 or 168 h after ischemic procedure (for Na+,K+ -ATPase activities measurement) or 2, 24, 48 or 168 h after ischemia (for SOD activities measurement). HBO procedure was repeated for 7 consecutive days. It was found that global cerebral ischemia induced a statistically significant decrease in the Na+,K+ -ATPase activity of the optic nerves, starting from 0.5 to 168 h of reperfusion. Maximal enzymatic inhibition was registered 24 h after the ischemic damage. The decline in the Na+,K+ -ATPase activity was prevented in the animals exposed to HBO treatment within the first 6 h of reperfusion. The results of the presented experiments demonstrated also a statistically significant increase in the SOD activity after 24, 48 and 168 h of reperfusion in the optic nerves of non-HBO-treated ischemic animals as well as in the ischemic animals treated with HBO. Our results indicate that global cerebral ischemia induced a significant alterations in the Na+,K+ -ATPase and SOD activities in the optic nerves during different periods of reperfusion. HBO treatment, started within the first 6 h of reperfusion, prevented ischemia-induced changes in the Na+,K+ -ATPase activity, while the level of the SOD activity in the ischemic animals was not changed after HBO administration.