Brain tissue responses to ischemia

Hypothermia and pediatric cardiac arrest

The survival outcome following pediatric cardiac arrest still remains poor. Survival to hospital discharge ranges anywhere from 0 to 38% when considering both out-of-hospital and in-hospital arrests, with up to 50% of the survivors having neurologic injury. The use of mild induced hypothermia has not been definitively proven to improve outcomes following pediatric cardiac arrest. This may be due to the lack of consensus regarding target temperature, best method of cooling, optimal duration of cooling and identifying the patient population who will receive the greatest benefit. We review the current applications of induced hypothermia in pediatric patients following cardiac arrest after searching the current literature through Pubmed and Ovid journal databases. We put forth compiled recommendations/guidelines for initiating hypothermia therapy, its maintenance, associated monitoring and suggested adjunctive therapies to produce favorable neurologic and survival outcomes.

Electro-acupuncture can alleviate the cerebral oedema of rat after ischemia

PRIMARY OBJECTIVE

This study was designed to determine whether electro-acupuncture (EA) could alleviate cerebral oedema after cerebral ischemia.

RESEARCH DESIGN

EA has been widely used for cerebrovascular disease in East Asian countries. However, whether EA might reduce cerebral oedema after stroke remains unclear. In the current study, diffusion-weighted MRI, which is a reliable method for detecting cerebral oedema, was used to determine whether EA could ameliorate cerebral oedema.

METHODS AND PROCEDURES

Twelve rats with induced strokes were divided into two groups: one group with EA treatment (EA group) and one group without EA treatment (non-EA group). Both groups of rats underwent MRI scanning at the same time point following ischemia.

MAIN OUTCOMES AND RESULTS

Diffusion-weighted imaging showed that the relative apparent diffusion coefficient increased significantly in the cortical and sub-cortical areas of the EA group relative to the non-EA group, indicating that EA can alleviate cerebral oedema after ischemic stroke.

CONCLUSIONS

Electro-acupuncture can alleviate cerebral oedema in rats following ischemia.

TRPM7 in cerebral ischemia and potential target for drug development in stroke

Searching for effective pharmacological agents for stroke treatment has largely been unsuccessful. Despite initial excitement, antagonists for glutamate receptors, the most studied receptor channels in ischemic stroke, have shown insufficient neuroprotective effects in clinical trials. Outside the traditional glutamate-mediated excitotoxicity, recent evidence suggests few non-glutamate mechanisms, which may also cause ionic imbalance and cell death in cerebral ischemia. Transient receptor potential melastatin 7 (TRPM7) is a Ca(2+) permeable, non-selective cation channel that has recently gained attention as a potential cation influx pathway involved in ischemic events. Compelling new evidence from an in vivo study demonstrated that suppression of TRPM7 channels in adult rat brain in vivo using virally mediated gene silencing approach reduced delayed neuronal cell death and preserved neuronal functions in global cerebral ischemia. In this review, we will discuss the current understanding of the role of TRPM7 channels in physiology and pathophysiology as well as its therapeutic potential in stroke.

Evaluation of brain and kidney energy metabolism in an animal model of contrast-induced nephropathy

Contrast-induced nephropathy is a common cause of acute renal failure in hospitalized patients, occurring from 24 to 48 h and up to 5 days after the administration of iodinated contrast media. Encephalopathy may accompany acute renal failure and presents with a complex of symptoms progressing from mild sensorial clouding to delirium and coma. The mechanisms responsible for neurological complications in patients with acute renal failure are still poorly known, but several studies suggest that mitochondrial dysfunction plays a crucial role in the pathogenesis of uremic encephalopathy. Thus, we measured mitochondrial respiratory chain complexes and creatine kinase activities in rat brain and kidney after administration of contrast media. Wistar rats were submitted to 6.0 ml/kg meglumine/sodium diatrizoate administration via the tail vein (acute renal failure induced by contrast media) and saline in an equal volume with the radiocontrast material (control group); 6 days after, the animals were killed and kidney and brain were obtained. The results showed that contrast media administration decreased complexes I and IV activities in cerebral cortex; in prefrontal cortex, complex I activity was inhibited. On the other hand, contrast media administration increased complexes I and II-III activities in hippocampus and striatum and complex IV activity in hippocampus. Moreover, that administration of contrast media also decreased creatine kinase activity in the cerebral cortex. The present findings suggest that the inhibition of mitochondrial respiratory chain complexes and creatine kinase caused by the acute renal failure induced by contrast media administration may be involved in the neurological complications reported in patients and might play a role in the pathogenesis of the encephalopathy caused by acute renal failure.

Neuroprotective effects of marine algae

The marine environment is known as a rich source of chemical structures with numerous beneficial health effects. Among marine organisms, marine algae have been identified as an under-exploited plant resource, although they have long been recognized as valuable sources of structurally diverse bioactive compounds. Presently, several lines of studies have provided insight into biological activities and neuroprotective effects of marine algae including antioxidant, anti-neuroinflammatory, cholinesterase inhibitory activity and the inhibition of neuronal death. Hence, marine algae have great potential to be used for neuroprotection as part of pharmaceuticals, nutraceuticals and functional foods. This contribution presents an overview of marine algal neuroprotective effects and their potential application in neuroprotection.

The optimal therapeutic timing and mechanism of puerarin treatment of spinal cord ischemia-reperfusion injury in rats

AIM OF THE STUDY

The purpose of this study was to explore the optimal therapeutic timing and mechanism of puerarin treatment of spinal cord ischemia-reperfusion injury.

MATERIALS AND METHODS

The spinal ischemia-reperfusion injury was conducted in male Sprague-Dawley rats, and 50mg/kg of puerarin was injected intraperitoneally at 1, 2, 4 and 6h after the injury. Motor function was measured 48 h after reperfusion started. Thioredoxin expression and apoptosis indices were determined.

RESULTS

Improvement of motor function at 1, 2, and 4h was demonstrated in the animals with puerarin treatment. Ischemia-reperfusion injury resulted in a decrease in the expression of thioredoxin, while puerarin administration elevated the expression of thioredoxin-1/thioredoxin-2 mRNA. Apoptosis indices were significantly reduced by puerarin administration.

CONCLUSIONS

We conclude that administration of puerarin within 4h of spinal ischemia-reperfusion injury reduces ischemic reperfusion damage, and that the neuroprotective effect of puerarin involves an increase in the transcription of thioredoxin and a reduction of apoptosis.

Pinocembrin attenuates blood-brain barrier injury induced by global cerebral ischemia-reperfusion in rats

Blood-brain barrier (BBB) disruption is a major consequence of cerebral ischemia/reperfusion. Several studies have reported the neuroprotection of pinocembrin on cerebral ischemia in vivo and in vitro, but the effects of pinocembrin on BBB and its underlying mechanisms are not clear. In this study, we investigated the effects of pinocembrin on BBB functions in the global cerebral ischemia/reperfusion (GCI/R) model in rats. Neurological scores and brain edema were evaluated. BBB permeability was assessed by detecting the concentrations of Evan's blue (EB) and fluorescein sodium (NaF) in brain tissue. The pathological changes of BBB ultrastructure were observed by transmission electron microscopy. Cerebral blood flow (CBF) was measured by laser Doppler flowmetry. The effects of pinocembrin on primary cultured rat cerebral microvascular endothelial cells (RCMECs) against oxygen-glucose deprivation/reoxygenation (OGD/R) were also investigated. The results showed pinocembrin decreased neurological score and lessened brain edema induced by GCI/R. Pinocembrin also reduced the concentrations of EB and NaF in brain tissue of the GCI/R rats. And pinocembrin alleviated the ultrastructural changes of cerebral microvessels, astrocyte end-feet and neurons, and improved CBF in the GCI/R rats. In addition, pinocembrin increased the viability and mitochondrial membrane potential of cultured RCMECs induced by OGD/R. In conclusion, these data demonstrate that pinocembrin alleviates blood-brain barrier injury induced by GCI/R in rats.

Neuroprotective signaling pathways are modulated by adenosine in the anoxia tolerant turtle

Cumulative evidence shows a protective role for adenosine A1 receptors (A1R) in hypoxia/ischemia; A1R stimulation reduces neuronal damage, whereas blockade exacerbates damage. The signal transduction pathways may involve the mitogen-activated protein kinase (MAPK) pathways and serine/threonine kinase (AKT), with cell survival depending on the timing and degree of upregulation of these cascades as well as the balance between pro-survival and pro-death pathways. Here, we show in vitro that extracellular signal-regulated kinase (ERK1/2) and phosphatidylinositol 3-kinase (PI3-K/AKT) activation is dependent on A1R stimulation, with further downstream effects that promote neuronal survival. Phosphorylated ERK1/2 (p-ERK) and AKT (p-AKT) as well as Bcl-2 are upregulated in anoxic neuronally enriched primary cultures from turtle brain. This native upregulation is further increased by the selective A1R agonist 2-chloro-N-cyclopentyladenosine (CCPA), whereas the selective antagonist 8-cyclopentyl-1,3-dihydropylxanthine (DPCPX) decreases p-ERK and p-AKT expression. Conversely, A1R antagonism resulted in increases in phosphorylated JNK (p-JNK), p38 (p-p38), and Bax. As pathological and adaptive changes occur simultaneously during anoxia/ischemia in mammalian neurons, the turtle provides an alternative model to analyze protective mechanisms in the absence of evident pathologies.

Mechanisms and prospects of ischemic tolerance induced by cerebral preconditioning

In the brain, brief episodes of ischemia induce tolerance against a subsequent severe episode of ischemia. This phenomenon of endogenous neuroprotection is known as preconditioning-induced ischemic tolerance. The purpose of this review is to summarize the current state of knowledge about mechanisms and potential applications of cerebral preconditioning and ischemic tolerance. Articles related to the terms ischemic preconditioning and ischemic tolerance were systematically searched via MEDLINE/PubMed, and articles published in English related to the nervous system were selected and analyzed. The past two decades have provided interesting insights into the molecular mechanisms of this neuroprotective phenomenon. Although both rapid and delayed types of tolerance have been documented in experimental settings, the delayed type has been found to be more prominent in the case of neuronal ischemic tolerance. Many intracellular signaling pathways have been implicated regarding ischemic preconditioning. Most of these are associated with membrane receptors, kinase cascades, and transcription factors. Moreover, ischemic tolerance can be induced by exposing animals or cells to diverse types of endogenous and exogenous stimuli that are not necessarily hypoxic or ischemic in nature. These cross-tolerances raise the hope that, in the future, it will be possible to pharmacologically activate or mimic ischemic tolerance in the human brain. Another promising approach is remote preconditioning in which preconditioning of one organ or system leads to the protection of a different (remote) organ that is difficult to target, such as the brain. The preconditioning strategy and related interventions can confer neuroprotection in experimental ischemia, and, thus, have promise for practical applications in cases of vascular neurosurgery and endo-vascular therapy.

H2S protects hippocampal neurons from anoxia-reoxygenation through cAMP-mediated PI3K/Akt/p70S6K cell-survival signaling pathways

The study aims to investigate the effect of hydrogen sulfide (H(2)S) on the phosphatidylinositol 3-kinase (PI3K)/Akt/p70 ribosomal S6 kinase (p70S6K) signal transduction pathway after oxygen glucose deprivation/reoxygenation (OGD/R) in the rat hippocampus. Newborn Wister rats were decapitated under anesthesia, and hippocampal tissue was dissected. Cells were plated at 1.0 × 10(5) cells/mL on polylysine-treated 96-well and 6-well plates. After 7 days in culture, cells were randomly assigned to six groups: control, OGD/R, sodium hydrosulfide (NaHS) following OGD/R, NaHS/triciribine following OGD/R, NaHS/rapamycin following OGD/R, and NaHS/triciribine/rapamycin following OGD/R. Neuronal purity and cell viability were assessed in each group, as well as apoptosis and expression of cyclic adenosine 3', 5'-monophosphate (cAMP), PI3K, Akt, and p70S6K. NaHS enhanced cAMP concentration and expression of PI3K, Akt, and p70S6K. In addition, neuronal viability was increased and apoptotic neuronal numbers decreased (P<0.01). Triciribine inhibited Akt and p70S6K, as well as decreased cell survival and viability compared with the NaHS group (P<0.05 or P<0.01). Rapamycin resulted in decreased p70S6K expression and neuronal viability, as well as increased number of apoptotic neurons compared with the NaHS group (P<0.05 or P<0.01). H(2)S acted via cAMP-mediated PI3K/Akt/p70S6K signal transduction pathways to inhibit hippocampal neuronal apoptosis and protect neurons from OGD/R-induced injury.

Long-lasting post-mortem activity of spinal microglia in situ in mice

As CNS macrophages, microglia show a high spontaneous motility of their processes, continuously surveying their microenvironment. Upon CNS injury, microglia react by immediate cellular polarization and process extension toward the lesion site as well as by subsequent amoeboid lesion-directed migration and phagocytosis. To determine the ability of microglia to fulfill their role within distinctively lesioned tissue in the absence of life support, we investigated microglial activity and responsiveness to laser-induced axonal injuries in the spinal dorsal columns in situ after cardiac and respiratory arrest, i.e., post-mortem, in the progressively degrading nervous tissue. For this purpose, we used time-lapse two-photon laser scanning microscopy in double transgenic mice expressing enhanced green fluorescent protein in microglia and enhanced yellow fluorescent protein in projection neurons. Depending on the premortal condition of the animal, microglial activity and responsiveness remain for up to5-10 hr post-mortem. Thereby, the continuously decreasing glial reaction is independent of oxygen and glucose supply but requires residual ATP, suggesting a parasitic form of energy, such as a transmembrane uptake of ATP released from injured nervous tissue. Even though initially microglia are able to detect axonal injury after disruption of the blood supply, the later aspects of glial reaction, for example amoeboid conversion and migration, are absent post- mortem, corresponding to the failure of microglia to prevent secondary damage after injury of nervous tissue.

Role of the NR2A/2B subunits of the N-methyl-D-aspartate receptor in glutamate-induced glutamic acid decarboxylase alteration in cortical GABAergic neurons in vitro

The vulnerability of brain neuronal cell subpopulations to neurologic insults varies greatly. Among cells that survive a pathological insult, for example ischemia or brain trauma, some may undergo morphological and/or biochemical changes that may compromise brain function. The present study is a follow-up of our previous studies that investigated the effect of glutamate-induced excitotoxicity on the GABA synthesizing enzyme glutamic acid decarboxylase (GAD65/67)'s expression in surviving DIV 11 cortical GABAergic neurons in vitro [Monnerie and Le Roux, (2007) Exp Neurol 205:367-382, (2008) Exp Neurol 213:145-153]. An N-methyl-D-aspartate receptor (NMDAR)-mediated decrease in GAD expression was found following glutamate exposure. Here we examined which NMDAR subtype(s) mediated the glutamate-induced change in GAD protein levels. Western blotting techniques on cortical neuron cultures showed that glutamate's effect on GAD proteins was not altered by NR2B-containing diheteromeric (NR1/NR2B) receptor blockade. By contrast, blockade of triheteromeric (NR1/NR2A/NR2B) receptors fully protected against a decrease in GAD protein levels following glutamate exposure. When receptor location on the postsynaptic membrane was examined, extrasynaptic NMDAR stimulation was observed to be sufficient to decrease GAD protein levels similar to that observed after glutamate bath application. Blocking diheteromeric receptors prevented glutamate's effect on GAD proteins after extrasynaptic NMDAR stimulation. Finally, NR2B subunit examination with site-specific antibodies demonstrated a glutamate-induced, calpain-mediated alteration in NR2B expression. These results suggest that glutamate-induced excitotoxic NMDAR stimulation in cultured GABAergic cortical neurons depends upon subunit composition and receptor location (synaptic vs. extrasynaptic) on the neuronal membrane. Biochemical alterations in surviving cortical GABAergic neurons in various disease states may contribute to the altered balance between excitation and inhibition that is often observed after injury.

Physiologically relevant online electrochemical method for continuous and simultaneous monitoring of striatum glucose and lactate following global cerebral ischemia/reperfusion

This study demonstrates a new electroanalytical method with a high physiological relevance for simultaneous online monitoring of glucose and lactate in the striatum of the rat brain following global cerebral ischemia/reperfusion. The online analytical method is based on the efficient integration of in vivo microdialysis sampling with an online selective electrochemical detection with the electrochemical biosensors with dehydrogenases, i.e., glucose and lactate dehydrogenases, as recognition elements. The dehydrogenase-based electrochemical biosensors are developed onto the dual split-disk plastic carbon film (SPCF) electrodes with methylene green (MG) adsorbed onto single-walled carbon nanotubes (SWNTs) as the electrocatalyst for the oxidation of dihydronicotiamide adenine dinucleotide (NADH) at a low potential of 0.0 V (vs Ag/AgCl). Artificial cerebrospinal fluid (aCSF) containing NAD(+) is externally perfused from a second pump and online mixed with the brain microdialysates to minimize the variation of pH that occurred following the cerebral ischemia/reperfusion and to supply NAD(+) cofactor and O(2) for the enzymatic reactions of dehydrogenases and ascorbate oxidase, respectively. As a result, the developed online electroanalytical method exhibits a high selectivity against the electrochemically active species endogenously existing in the cerebral systems and a high tolerance against the variation of pH and O(2) following cerebral ischemia/reperfusion. This property, along with the good linearity and a high stability toward glucose and lactate as well as little cross-talk between two biosensors, substantially makes this method possible for the continuous, simultaneous, and online monitoring of glucose and lactate in the rat brain following global cerebral ischemia/reperfusion. This study establishes a new and effective platform for the investigation of the energy metabolism in physiological and pathological processes.

Evaluation of mitochondrial respiratory chain in the brain of rats after pneumococcal meningitis

The brain is highly dependent on ATP and most cell energy is obtained through oxidative phosphorylation, a process requiring the action of various respiratory enzyme complexes located in a special structure of the inner mitochondrial membrane. Bacterial meningitis due to Streptococcus pneumoniae is associated with a significant mortality rate and persisting neurologic sequelae including sensory-motor deficits, seizures, and impairments of learning and memory. In this context, we evaluated the activities of mitochondrial respiratory chain complexes in the brain of rats submitted to meningitis by S. pneumoniae inoculation into the cisterna magna. Our results demonstrated that complex I activity was not altered in cerebral cortex after meningitis; complexes II, III and IV were increased 24 and 48h after meningitis. We have also verified that complex I was inhibited in prefrontal cortex 48h after meningitis; complexes II, III and IV were not altered. Our results also demonstrated that complex I activity was inhibited in striatum, hippocampus and cerebellum 24h after meningitis. Moreover, complex II activity was increased in hippocampus and striatum 24 and 48h after meningitis; complexes III and IV activity were increased in striatum, hippocampus and cerebellum 48h after meningitis. Taking together previous reports and our present findings, we speculate that oxidative stress and metabolism impairment might contribute, at least in part, for the pathogenesis of pneumococcal meningitis.

Imaging mass spectrometry revealed the production of lyso-phosphatidylcholine in the injured ischemic rat brain

To develop an effective neuroprotective strategy against ischemic injury, it is important to identify the key molecules involved in the progression of injury. Direct molecular analysis of tissue using mass spectrometry (MS) is a subject of much interest in the field of metabolomics. Most notably, imaging mass spectrometry (IMS) allows visualization of molecular distributions on the tissue surface. To understand lipid dynamics during ischemic injury, we performed IMS analysis on rat brain tissue sections with focal cerebral ischemia. Sprague-Dawley rats were sacrificed at 24 h after middle cerebral artery occlusion, and brain sections were prepared. IMS analyses were conducted using matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI-TOF MS) in positive ion mode. To determine the molecular structures, the detected ions were subjected to tandem MS. The intensity counts of the ion signals of m/z 798.5 and m/z 760.5 that are revealed to be a phosphatidylcholine, PC (16:0/18:1) are reduced in the area of focal cerebral ischemia as compared to the normal cerebral area. In contrast, the signal of m/z 496.3, identified as a lyso-phosphatidylcholine, LPC (16:0), was clearly increased in the area of focal cerebral ischemia. In IMS analyses, changes of PC (16:0/18:1) and LPC (16:0) are observed beyond the border of the injured area. Together with previous reports--that PCs are hydrolyzed by phospholipase A(2) (PLA(2)) and produce LPCs,--our present results suggest that LPC (16:0) is generated during the injury process after cerebral ischemia, presumably via PLA(2) activation, and that PC (16:0/18:1) is one of its precursor molecules.

Early ischemia enhances action potential-dependent, spontaneous glutamatergic responses in CA1 neurons

Two types of quantal spontaneous neurotransmitter release are present in the nervous system, namely action potential (AP)-dependent release and AP-independent release. Previous studies have identified and characterized AP-independent release during hypoxia and ischemia. However, the relative contribution of AP-dependent spontaneous release to the overall glutamate released during transient ischemia has not been quantified. Furthermore, the neuronal activity that mediates such release has not been identified. Using acute brain slices, we show that AP-dependent release constitutes approximately one-third of the overall glutamate-mediated excitatory postsynaptic potentials/currents (EPSPs/EPSCs) measured onto hippocampal CA1 pyramidal neurons. However, during transient (2 mins) in vitro hypoxia-hypoglycemia, large-amplitude, AP-dependent spontaneous release is significantly enhanced and contributes to 74% of the overall glutamatergic responses. This increased AP-dependent release is due to hyper-excitability in the presynaptic CA3 neurons, which is mediated by the activity of NMDA receptors. Spontaneous glutamate release during ischemia can lead to excitotoxicity and perturbation of neural network functions.

MicroRNA expression changes in the hippocampi of rats subjected to global ischemia

The hippocampus is particularly vulnerable to ischemia, which is accompanied by substantial alterations in gene expression. Recent studies show that microRNAs extensively mediate post-transcriptional gene expression. However, the regulatory mechanisms in the hippocampus that microRNAs participate in remain unclear. Here, we used microarray analysis to characterize the microRNA expression profile in rat hippocampus and to identify changes in expression after 20 minutes of global ischemia followed by either 30 minutes or 24 hours of reperfusion. In the normal hippocampus, we detected 286 microRNAs, of which the let-7 family accounted for 32%. After ischemia followed by 30 minutes of reperfusion, 23 microRNAs were upregulated and 32 were downregulated; after 24 hours of reperfusion 40 were upregulated and 31 were downregulated. These results suggest that several microRNAs may be involved in regulating the normal physiological activity of the hippocampus and its response to ischemia and reperfusion.

Interleukin-6 plasmatic levels in patients with head trauma and intracerebral hemorrhage

The exact role of inflammatory response in hemorrhagic contusions is not fully characterized. The present study quantified IL-6 plasmatic levels in patients with closed head trauma and hemorrhagic contusions during the first 6 to 12 hours postrauma. The association between the plasmatic IL-6 levels, severity of trauma according to the Glasgow Coma Scale, volume of intracerebral hemorrhage and patient's clinical evolution were investigated. Although inflammation is a multifactorial process, a strong correlation between IL-6 levels, volume of traumatic hemorrhage and in-hospital evolution could be observed. A correlation between the IL-6 levels quantified 6 hours postrauma and progression of lesion volume between admission and 12 hours postrauma is suggested. The present study reinforces the importance of IL-6 in influencing the clinical conditions of a patient with cerebral injuries, particularly hemorrhagic contusions.

The effect of mitochondrial adenosine triphosphate-sensitive potassium (K(ATP)) channel blocker on ischemic preconditioning in hypoxic-ischemic brain injury model of neonatal rat

BACKGROUND

A brief episode of cerebral ischemia confers transient ischemic tolerance to a subsequent ischemic challenge that is otherwise lethal to them. This study was purposed to evaluate the effect of mitochondrial adenosine triphosphate-sensitive potassium (KATP) channel blocker on ischemic preconditioning in hypoxic-ischemic brain injury model of neonatal rat.

METHODS

Seven-day old Sprague-Dawley rat pups were used. The rats were divided into five groups; control group (n = 91), pretreatment hypoxic preconditioning group (n = 43), pretreatment ischemic preconditioning group (n = 52), hypoxic preconditioning group (n = 39), and ischemic preconditioning group (n = 51). Rats in the pretreatment hypoxic preconditioning group and pretreatment ischemic preconditioning group were treated by an intraperitoneal injection with 5-hydroxydecanoate (60 mg/kg). Thirty minutes after injection, right common carotid artery was temporarily occluded for ten minutes in pretreatment ischemic preconditioning group. Rats in the pretreatment hypoxic preconditioning group and hypoxic preconditioning group underwent hypoxia (8% oxygen/92% nitrogen) for four hours. Twenty-four hours after the preconditioning, rats from all groups were exposed to right common carotid artery ligation followed by 2.5 hour hypoxia. On the 1st day after hypoxic-ischemic brain injury, terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling (TUNEL) reaction was evaluate as apoptotic markers and triphenyl tetrazolium chloride (TTC) was done to measure necrotic tissue. All rats were sacrificed 2 weeks after hypoxic-ischemia brain injury and the brains were examined for morphologic study.

RESULTS

There were no differenced in survival rate, infarct area, number of TUNEL positive cells and morphologic score either between hypoxic preconditioning group and pretreatment hypoxic preconditioning group or between ischemic preconditioning group and pretreatment ischemic preconditioning group.

CONCLUSIONS

The results suggests that mitochondrial K(ATP) channel blocker, 5-hydroxydecanoate, does not change hypoxic-ischemic preconditioning in the neonatal rat.

Digoxin may provide protection against vasospasm in subarachnoid haemorrhage

BACKGROUND

Vasospasm is a significant reason for poor clinical outcome in subarachnoid haemorrhage (SAH). One of the possible causes of vasospasm is attributed to the inhibition of Na(+)/K(+)-ATPase and increased intracellular calcium. Although digoxin, a cardiac glycoside (CG), inhibits the Na(+)/K(+)-ATPase, diverse and contradictory biological actions of CGs have also been reported. This study aimed to investigate the effect of digoxin on an experimental vasospasm after subarachnoid haemorrhage (SAH) in rats.

METHODS

The rats used in the study were divided into normal, saline, SAH, and drug groups. A double-haemorrhage method was applied for the SAH groups. Normal saline or blood samples were injected into the cisterna magna. No surgical procedures were performed on the normal group. For the drug groups, daily digoxin was administered intraperitoneally after saline or blood injections. On days 3 and 7 after injections, the brains and basilar artery sections of all the groups were prepared for light-microscopic examination. The wall thickness and luminal area of the basilar artery were calculated by using medical imaging software.

RESULTS

Increased wall thickness and reduced vessel luminal area were conspicuously significant in the SAH groups which did not receive digoxin. In SAH groups after digoxin administration, the vessel wall thickness decreased, and no significant change was found in vessel wall thickness when compared with the normal and saline groups. The vessel luminal area was not reduced in SAH after digoxin administration.

CONCLUSIONS

These results suggest that digoxin administration in experimental SAH may have a beneficial effect on the protection against vasospasm. If further investigations support our results, the present study may offer a new insight into the treatment of SAH.

Postischemic PKC activation rescues retrograde and anterograde long-term memory

Therapeutics for cerebral ischemia/hypoxia, which often results in ischemic stroke in humans, are a global unmet medical need. Here, we report that bryostatin-1, a highly potent protein kinase C (PKC) activator, interrupts pathophysiological molecular cascades and apoptosis triggered by cerebral ischemia/hypoxia, enhances neurotrophic activity, and induces synaptogenesis in rats. This postischemic therapeutic approach is further shown to preserve learning and memory capacity even 4 months later as well as long-term memory induced before the ischemic event. Our results of electromicroscopic and immunohistochemical analyses of neuronal and synaptic ultra-structure are consistent with a PKC-mediated synaptic remodeling and repair process that confers long-lasting preservation of spatial learning and memory before and after the cerebral ischemic/hypoxic event, suggesting a previously undescribed therapeutic modality for cerebral ischemia/hypoxia and ischemic stroke.

Adenosine deaminase activity, lipid peroxidation and astrocyte responses in the cerebral cortex of rats after neonatal hypoxia ischemia

Hypoxia ischemia (HI) is a common cause of damage in the fetal and neonatal brain. Lifelong disabilities such as cerebral palsy, epilepsy, behavioral and learning disorders are some of the consequences of brain injury acquired in the perinatal periods. Inflammation and formation of free radicals appear to play key roles in neonatal HI. The aim of this study was to describe the chronological sequence of adenosine deaminase (ADA) activity, the oxidative damage changes and astrocyte response using the classic model of neonatal HI. We observed an increase in the activity of ADA and lipid peroxidation in the cerebral cortex 8 days after neonatal HI. This was accompanied by a GFAP-positive, and the degree of brain damage was determined histochemically by hematoxylin-eosin (HE). Taking into account the important anti-inflammatory role of adenosine, ADA may provide an efficient means for scavenging cell-surrounding adenosine and play an important part in subsequent events of neonatal HI in association with GFAP reactive gliosis. The present investigation showed that neonatal HI causes the increase of free radicals and significant damage in the cerebral cortex. The increase in ADA activity may reflect the activation of the immune system caused by HI because the morphological analysis exhibited a lymphocytic infiltration.

Bipolar disorder and mechanisms of action of mood stabilizers

Bipolar disorder (BD) is a major medical and social burden, whose cause, pathophysiology and treatment are not agreed on. It is characterized by recurrent periods of mania and depression (Bipolar I) or of hypomania and depression (Bipolar II). Its inheritance is polygenic, with evidence of a neurotransmission imbalance and disease progression. Patients often take multiple agents concurrently, with incomplete therapeutic success, particularly with regard to depression. Suicide is common. Of the hypotheses regarding the action of mood stabilizers in BD, the "arachidonic acid (AA) cascade" hypothesis is presented in detail in this review. It is based on evidence that chronic administration of lithium, carbamazepine, sodium valproate, or lamotrigine to rats downregulated AA turnover in brain phospholipids, formation of prostaglandin E(2), and/or expression of AA cascade enzymes, including cytosolic phospholipase A(2), cyclooxygenase-2 and/or acyl-CoA synthetase. The changes were selective for AA, since brain docosahexaenoic or palmitic acid metabolism, when measured, was unaffected, and topiramate, ineffective in BD, did not modify the rat brain AA cascade. Downregulation of the cascade by the mood stabilizers corresponded to inhibition of AA neurotransmission via dopaminergic D(2)-like and glutamatergic NMDA receptors. Unlike the mood stabilizers, antidepressants that increase switching of bipolar depression to mania upregulated the rat brain AA cascade. These observations suggest that the brain AA cascade is a common target of mood stabilizers, and that bipolar symptoms, particularly mania, are associated with an upregulated cascade and excess AA signaling via D(2)-like and NMDA receptors. This review presents ways to test these suggestions.

Calpain-mediated N-cadherin proteolytic processing in brain injury

Neural-cadherin (N-cadherin), a member of the classical cadherin family of transmembrane glycoproteins, mediates cellular recognition and cell-cell adhesion through calcium-dependent homophilic interactions and plays important roles in the development and maintenance of the nervous system. Metalloproteinase is known to cleave N-cadherin, which is further cleaved by gamma-secretase. The intracellular domain of N-cadherin interacts with beta-catenin, and beta-catenin stability is critical for cell-cell adhesion and cell survival. In the present study, we showed that N-cadherin is cleaved specifically by calpain, resulting in the generation of a novel 110 kDa fragment. The cleavage occurred in ischemic brain lesions and in vitro neural cells in the presence of NMDA and ionomycin, and was restored by calpain inhibitors but not matrix metalloproteinase or gamma-secretase inhibitors. Calpain directly cleaved N-cadherin in in vitro calpain assays, and calpain inhibitors prevented its cleavage in a dose-dependent manner. Using N-cadherin deletion mutants, we found that calpain cleavage sites exist in at least four regions of the cytoplasmic domain. Treatment with NMDA induced neuronal death, and it suppressed the expression of surface N-cadherin and the N-cadherin/beta-catenin interaction, effects that were prevented by calpain inhibitor. Furthermore, calpain-mediated N-cadherin cleavage significantly affected cell-cell adhesion, AKT signaling, the N-cadherin/beta-catenin interaction and the Wnt target gene expressions through the accumulation of nuclear beta-catenin.

Edaravone for the treatment of acute cerebral infarction: role of endothelium-derived nitric oxide and oxidative stress

Thrombolytic therapy is the most effective therapeutic strategy for the prevention of brain injury and reduction of mortality in patients with acute cerebral infarction. A combination of established thrombolytic therapy and effective neuronal protection therapy has more beneficial effects for patients with acute cerebral infarction. Edaravone (chemical name: 3-methyl-1-phenyl-2-pyrazolin-5-one) is a strong, novel scavenger of free radicals. Several lines of evidence have shown that edaravone has preventive effects on brain injury following ischaemia and reperfusion in patients with brain attack. This review focuses on putative mechanisms underlying the beneficial effects of edaravone on the atherosclerotic process in patients with stroke and on the possibility of edaravone-induced extension of the therapeutic time window in patients with acute cerebral infarction.

Neuroprotection of ethanol against cerebral ischemia/reperfusion induced brain injury through GABA receptor activation

In this study we investigated whether ethanol could play neuroprotective effects against ischemic brain injury and the related mechanism. Cresyl violet staining results demonstrated that moderate dose of ethanol administered intracerebroventricularly (i.c.v.) had neuroprotective effect against ischemia-reperfusion induced neuronal cell death. Ethanol also inhibited the phosphorylation of JNK3 induced by cerebral ischemia-reperfusion. Three separate drugs, NS3763 (the selective antagonist of GluR5), GluR5 antisense oligodeoxynucleotides (AS-ODNs) and Bicuculline (an antagonist of GABA receptors), were found to inhibit the neuroprotective effect of ethanol. Moreover, the GABA receptor agonist muscimol could attenuate the JNK3 phosphorylation. Taken together, the results suggest that during ischemia-reperfusion ethanol may activate presynaptic GluR5-KA and postsynaptic GABA receptors continuously, and the activation of GABA receptors inhibits the JNK3 signal pathway. The results show a novel potential mechanism underlying ethanol protective effects.

Nicotinamide prevents NAD+ depletion and protects neurons against excitotoxicity and cerebral ischemia: NAD+ consumption by SIRT1 may endanger energetically compromised neurons

Neurons require large amounts of energy to support their survival and function, and are therefore susceptible to excitotoxicity, a form of cell death involving bioenergetic stress that may occur in several neurological disorders including stroke and Alzheimer's disease. Here we studied the roles of NAD(+) bioenergetic state, and the NAD(+)-dependent enzymes SIRT1 and PARP-1, in excitotoxic neuronal death in cultured neurons and in a mouse model of focal ischemic stroke. Excitotoxic activation of NMDA receptors induced a rapid decrease of cellular NAD(P)H levels and mitochondrial membrane potential. Decreased NAD(+) levels and poly (ADP-ribose) polymer (PAR) accumulation in nuclei were relatively early events (<4 h) that preceded the appearance of propidium iodide- and TUNEL-positive cells (markers of necrotic cell death and DNA strand breakage, respectively) which became evident by 6 h. Nicotinamide, an NAD(+) precursor and an inhibitor of SIRT1 and PARP1, inhibited SIRT1 deacetylase activity without affecting SIRT1 protein levels. NAD(+) levels were preserved and PAR accumulation and neuronal death induced by excitotoxic insults were attenuated in nicotinamide-treated cells. Treatment of neurons with the SIRT1 activator resveratrol did not protect them from glutamate/NMDA-induced NAD(+) depletion and death. In a mouse model of focal cerebral ischemic stroke, NAD(+) levels were decreased in both the contralateral and ipsilateral cortex 6 h after the onset of ischemia. Stroke resulted in dynamic changes of SIRT1 protein and activity levels which varied among brain regions. Administration of nicotinamide (200 mg/kg, i.p.) up to 1 h after the onset of ischemia elevated brain NAD(+) levels and reduced ischemic infarct size. Our findings demonstrate that the NAD(+) bioenergetic state is critical in determining whether neurons live or die in excitotoxic and ischemic conditions, and suggest a potential therapeutic benefit in stroke of agents that preserve cellular NAD(+) levels. Our data further suggest that, SIRT1 is linked to bioenergetic state and stress responses in neurons, and that under conditions of reduced cellular energy levels SIRT1 enzyme activity may consume sufficient NAD(+) to nullify any cell survival-promoting effects of its deacetylase action on protein substrates.

The effect of extracellular glutamate release on repetitive transient ischemic injury in global ischemia model

During operations, neurosurgeons usually perform multiple temporary occlusions of parental artery, possibly resulting in the neuronal damage. It is generally thought that neuronal damage by cerebral ischemia is associated with extracellular concentrations of the excitatory amino acids. In this study, we measured the dynamics of extracellular glutamate release in 11 vessel occlusion (VO) model to compare between single occlusion and repeated transient occlusions within short interval. Changes in cerebral blood flow were monitored by laser-Doppler flowmetry simultaneously with cortical glutamate level measured by amperometric biosensor. From real time monitoring of glutamate release in 11 VO model, the change of extracellular glutamate level in repeated transient occlusion group was smaller than that of single occlusion group, and the onset time of glutamate release in the second ischemic episode of repeated occlusion group was delayed compared to the first ischemic episode which was similar to that of single 10 min ischemic episode. These results suggested that repeated transient occlusion induces less glutamate release from neuronal cell than single occlusion, and the delayed onset time of glutamate release is attributed to endogeneous protective mechanism of ischemic tolerance.

PPARs as new therapeutic targets for the treatment of cerebral ischemia/reperfusion injury

Stroke is a leading cause of death and long-term disability in industrialized countries. Despite advances in understanding its pathophysiology, little progress has been made in the treatment of stroke. The currently available therapies have proven to be highly unsatisfactory (except thrombolysis) and attempts are being made to identify and characterize signaling proteins which could be exploited to design novel therapeutic modalities. The peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that control lipid and glucose metabolism. PPARs regulate gene expression by binding with the retinoid X receptor (RXR) as a heterodimeric partner to specific DNA sequences, termed PPAR response elements. In addition, PPARs may modulate gene transcription also by directly interfering with other transcription factor pathways in a DNA-binding independent manner. To date, three different PPAR isoforms, designated alpha, beta/delta, and gamma, have been identified. Recently, they have been found to play an important role for the pathogenesis of various disorders of the central nervous system and accumulating data suggest that PPARs may serve as potential targets for treating ischemic stroke. Activation of all PPAR isoforms, but especially of PPARgamma, was shown to prevent post-ischemic inflammation and neuronal damage in several in vitro and in vivo models, negatively regulating the expression of genes induced by ischemia/ reperfusion (I/R). This paper reviews the evidence and recent developments relating to the potential therapeutic effects of PPAR-agonists in the treatment of cerebral I/R injury.

Activation of EP2 prostanoid receptors in human glial cell lines stimulates the secretion of BDNF

Prostaglandin E(2) (PGE(2)) is produced at high levels in the injured central nervous system, where it is generally considered a cytotoxic mediator of inflammation. The cellular actions of PGE(2) are mediated by G-protein signaling activated by prostanoid receptors termed EP(1), EP(2), EP(3) and EP(4). Recent studies have implicated the EP(2) prostanoid receptor to be in apparently conflicting roles promoting neuronal death in some model systems and the survival of neurons in others. Here we show that treatment of immortalized human microglia and CCF-STTG1 astrocytes with either PGE(2) or the EP(2) selective agonist butaprost stimulates the release of brain-derived neurotrophic factor (BDNF). Both cell lines express mRNA for the EP(2) receptor, whereas transcripts for the other subtypes are not detected. Pharmacological studies using PGE(2) and modulators of cyclic AMP signaling implicate this pathway in PGE(2)-stimulated BDNF release. These results indicate that EP(2) prostanoid receptor activation induces BDNF secretion through stimulation of cyclic AMP dependent signaling. Our findings provide a mechanism by which endogenous PGE(2) might contribute to either neurotoxicity or neuroprotection in the injured brain via the induction of BDNF release from microglial cells and astrocytes.

Stem cells downregulate the elevated levels of tissue plasminogen activator in rats after spinal cord injury

We investigated the involvement of tPA after SCI in rats and effect of treatment with human umbilical cord blood derived stem cells. tPA expression and activity were determined in vivo after SCI in rats and in vitro in rat embryonic spinal neurons in response to injury with staurosporine, hydrogen peroxide and glutamate. The activity and/or expression of tPA increased after SCI and reached peak levels on day 21 post-SCI. Notably, the tPA mRNA activity was upregulated by 310-fold compared to controls on day 21 post-SCI. As expected, MBP expression is minimal at the time of peak tPA activity and vice versa. Implantation of hUCB after SCI resulted in the downregulation of elevated tPA activity/expression in vivo in rats as well as in vitro in spinal neurons. Our results demonstrated the involvement of tPA in the secondary pathogenesis after SCI as well as the therapeutic potential of hUCB.

Protective effect of tetraethyl pyrazine against focal cerebral ischemia/reperfusion injury in rats: therapeutic time window and its mechanism

INTRODUCTION

Tetramethyl pyrazine has been considered an effective agent in treating neurons ischemia/reperfusion injury, but the mechanism of its therapeutic effect remains unclear. This study was to explore the therapeutic time window and mechanism of tetramethyl pyrazine on temporary focal cerebral ischemia/reperfusion injury.

MATERIALS AND METHODS

Middle cerebral artery occlusion was conducted in male Sprague-Dawley rats and 20 mg/kg of tetramethyl pyrazine was intraperitoneally injected at different time points. At 72 h after reperfusion, all animals' neurologic deficit scores were evaluated. Cerebrums were removed and cerebral infarction volume was measured. The expression of thioredoxin and thioredoxin reductase mRNA was determined at 6 and 24 h after reperfusion.

RESULTS

Cerebral infarction volume and neurological deficit scores were significantly decreased in the group with tetramethyl pyrazine treatment. The expression of thioredoxin-1/thioredoxin-2 and thioredoxin reductase-1/thioredoxin reductase-2 was significantly decreased in rats with ischemia/reperfusion injury, while it was increased by tetramethyl pyrazine administration.

CONCLUSIONS

Treatment with tetramethyl pyrazine, within 4 h after reperfusion, protects the brain from ischemic reperfusion injury in rats. The neuroprotective mechanism of tetramethyl pyrazine treatment is, in part, mediated through the upregulation of thioredoxin transcription.

Ethanol alters the physiology of neuron-glia communication

In the central nervous system (CNS), both neurones and astrocytes play crucial roles. On a cellular level, brain activity involves continuous interactions within complex cellular circuits established between neural cells and glia. Although it was initially considered that neurones were the major cell type in cerebral function, nowadays astrocytes are considered to contribute to cerebral function too. Astrocytes support normal neuronal activity, including synaptic function, by regulating the extracellular environment with respect to ions and neurotransmitters. There is a plethora of noxious agents which can lead to the development of alterations in organs and functional systems, and that will end in a chronic prognosis. Among the potentially harmful external agents we can find ethanol consumption, whose consequences have been recognized as a major public health concern. Deregulation of cell cycle has devastating effects on the integrity of cells, and has been closely associated with the development of pathologies which can lead to dysfunction and cell death. An alteration of normal neuronal-glial physiology could represent the basis of neurodegenerative processes. In this review we will pay attention on to the recent findings in astrocyte function and their role toward neurons under ethanol consumption.

Rapid reversal of human intestinal ischemia-reperfusion induced damage by shedding of injured enterocytes and reepithelialisation

Background

Intestinal ischemia-reperfusion (IR) is a phenomenon related to physiological conditions (e.g. exercise, stress) and to pathophysiological events (e.g. acute mesenteric ischemia, aortic surgery). Although intestinal IR has been studied extensively in animals, results remain inconclusive and data on human intestinal IR are scarce. Therefore, an experimental harmless model for human intestinal IR was developed, enabling us to clarify the sequelae of human intestinal IR for the first time.

Methods and Findings

In 30 patients undergoing pancreatico-duodenectomy we took advantage of the fact that in this procedure a variable length of jejunum is removed. Isolated jejunum (5 cm) was subjected to 30 minutes ischemia followed by reperfusion. Intestinal Fatty Acid Binding Protein (I-FABP) arteriovenous concentration differences across the bowel segment were measured before and after ischemia to assess epithelial cell damage. Tissue sections were collected after ischemia and at 25, 60 and 120 minutes reperfusion and stained with H&E, and for I-FABP and the apoptosis marker M30. Bonferroni's test was used to compare I-FABP differences. Mean (SEM) arteriovenous concentration gradients of I-FABP across the jejunum revealed rapidly developing epithelial cell damage. I-FABP release significantly increased from 290 (46) pg/ml before ischemia towards 3,997 (554) pg/ml immediately after ischemia (p<0.001) and declined gradually to 1,143 (237) pg/ml within 1 hour reperfusion (p<0.001). Directly after ischemia the intestinal epithelial lining was microscopically normal, while subepithelial spaces appeared at the villus tip. However, after 25 minutes reperfusion, enterocyte M30 immunostaining was observed at the villus tip accompanied by shedding of mature enterocytes into the lumen and loss of I-FABP staining. Interestingly, within 60 minutes reperfusion the epithelial barrier resealed, while debris of apoptotic, shedded epithelial cells was observed in the lumen. At the same time, M30 immunoreactivity was absent in intact epithelial lining.

Conclusions

This is the first human study to clarify intestinal IR induced cell damage and repair and its direct consequences. It reveals a unique, endogenous clearing mechanism for injured enterocytes: rapid detachment of damaged apoptotic enterocytes into the lumen. This process is followed by repair of the epithelial continuity within an hour, resulting in a normal epithelial lining.

Neuroprotection by cord blood stem cells against glutamate-induced apoptosis is mediated by Akt pathway

The neurotransmitter glutamate mediates excitatory synaptic transmission in the brain and spinal cord. In pathological conditions massive glutamate release reaches near millimolar concentrations in the extracellular space and contributes to neuron degeneration and death. In the present study, we demonstrate a neuroprotective role for human umbilical cord blood stem cells (hUCB) against glutamate-induced apoptosis in cultured rat cortical neurons. Microarray analysis shows the upregulation of stress pathway genes after glutamate toxicity of neurons, while in cocultures with hUCB, survival pathway genes were upregulated. Real time-PCR analysis shows the expression of genes for NMDA receptors after glutamate toxicity in neurons. The neuroprotection of hUCB against glutamate toxicity is similar to the application of the glutamate receptor antagonist MK-801. Cocultures of hUCB protected neurons against glutamate-induced apoptosis as revealed by APO-BrdU TUNEL and FACS analyses. Immunoblot analysis shows that apoptosis is mediated by the cleavage of caspase-3 and caspase-7 in glutamate treated neurons. Cocultures with hUCB indicate the upregulation of Akt signaling pathway to protect neurons. Blocking of the Akt pathway by a dominant-negative Akt and using Akt-inhibitor IV, we confirm that the mechanism underlying hUCB neuroprotection involves activation of Akt signaling pathway. These results suggest the neuroprotective potential of hUCB against glutamate-induced apoptosis of cultured cortical neurons.

Early increase of Nox4 NADPH oxidase and superoxide generation following endothelin-1-induced stroke in conscious rats

Oxidative stress contributes to the progression of brain injury following ischemic stroke and reperfusion. NADPH oxidase is a well-established source of superoxide in vascular disease, but its contribution to tissue injury following ischemic stroke has yet to be fully elucidated. Here we show the spatiotemporal profile of NADPH oxidase subunits Nox2 and Nox4 and concurrent superoxide generation following stroke induced by middle cerebral artery constriction in conscious rats. Nox2 mRNA was progressively up-regulated in both the ipsilateral cortex and the striatum from 6 hr to 7 days poststroke and reperfusion. Nox4 mRNA was also up-regulated transiently in the cortex at 6 hr poststroke but returned to control levels after this time. In situ detection of superoxide generation with dihydroethidium fluorescence revealed an increase in superoxide within the ischemic core at 6 hr poststroke that was mostly colocalized with the neuronal marker NeuN. By 24 hr, this increase in superoxide production had spread to the boundary zone of the infarct, whereas it disappeared in the ischemic core as neuronal numbers declined. Subsequently, superoxide within the ischemic core again increased at 7 days and was mostly colocalized with the activated microglia/macrophage marker OX-42. Immunoreactivity to Nox2 followed the same spatiotemporal pattern as that of OX-42 immunostaining poststroke. Clearly, NADPH oxidase is an important mediator of oxidative stress and contributes to the progression of brain damage beyond the infarct core, via the activation of two catalytic subunits, Nox2 and Nox4. Selectively blocking these subunits might be useful for intervening in the progression of stroke brain injury.

Neuroprotection of GluR5-containing kainate receptor activation against ischemic brain injury through decreasing tyrosine phosphorylation of N-methyl-D-aspartate receptors mediated by Src kinase

Previous studies indicate that cerebral ischemia breaks the dynamic balance between excitatory and inhibitory inputs. The neural excitotoxicity induced by ionotropic glutamate receptors gain the upper hand during ischemia-reperfusion. In this paper, we investigate whether GluR5 (glutamate receptor 5)-containing kainate receptor activation could lead to a neuroprotective effect against ischemic brain injury and the related mechanism. The results showed that (RS)-2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA), a selective GluR5 agonist, could suppress Src tyrosine phosphorylation and interactions among N-methyl-D-aspartate (NMDA) receptor subunit 2A (NR2A), postsynaptic density protein 95 (PSD-95), and Src and then decrease NMDA receptor activation through attenuating tyrosine phosphorylation of NR2A and NR2B. More importantly, ATPA had a neuroprotective effect against ischemia-reperfusion-induced neuronal cell death in vivo. However, four separate drugs were found to abolish the effects of ATPA. These were selective GluR5 antagonist NS3763; GluR5 antisense oligodeoxynucleotides; CdCl(2), a broad spectrum blocker of voltage-gated calcium channels; and bicuculline, an antagonist of gamma-aminobutyric acid A (GABA(A)) receptor. GABA(A) receptor agonist muscimol could attenuate Src activation and interactions among NR2A, PSD-95 and Src, resulting the suppression of NMDA receptor tyrosine phosphorylation. Moreover, patch clamp recording proved that the activated GABA(A) receptor could inhibit NMDA receptor-mediated whole-cell currents. Taken together, the results suggest that during ischemia-reperfusion, activated GluR5 may facilitate Ca(2+)-dependent GABA release from interneurons. The released GABA can activate postsynaptic GABA(A) receptors, which then attenuates NMDA receptor tyrosine phosphorylation through inhibiting Src activation and disassembling the signaling module NR2A-PSD-95-Src. The final result of this process is that the pyramidal neurons are rescued from hyperexcitability.