The highly selective cyclooxygenase-2 inhibitor DFU is neuroprotective when given several hours after transient cerebral ischemia in gerbils

Several studies suggest that cyclooxygenase-2 contributes to the delayed progression of ischemic brain damage. In this study we examined whether the highly selective cyclooxygenase-2 inhibitor DFU reduces neuronal damage when administered several hours after 5 min of transient forebrain ischemia in gerbils. The extent of ischemic injury was assessed behaviorally by measuring the increases in locomotor activity and by histopathological evaluation of the extent of CA1 hippocampal pyramidal cell injury 7 days after ischemia. DFU treatment (10 mg/kg, p.o.) significantly reduced hippocampal neuronal damage even if the treatment is delayed until 12 h after ischemia. These results suggest that selective cyclooxygenase-2 inhibitors may be a valuable therapeutic strategy for ischemic brain injury.     

Astressin, a novel and potent CRF antagonist, is neuroprotective in the hippocampus when administered after a seizure

Corticotropin-releasing factor (CRF), the principle hypothalamic regulator of the adrenocortical axis, also functions as a neurotransmitter. In this latter role, CRF causes electrophysiological activation and epileptiform activity in various brain regions. That finding, coupled with the observation that CRF mRNA is induced in endangered brain regions following necrotic insults, suggests that the peptide might contribute to necrotic neuron loss. Supporting that, a number of studies have shown that CRF antagonists decrease ischemic or excitotoxic damage to neurons. In the present report, we demonstrate the considerable neuroprotective potential of a novel and potent CRF antagonist, astressin, against kainic acid-induced excitotoxic seizures. Intracerebroventricular infusion of the peptide both 30 min before and 10 min after seizures decreased damage in some hippocampal cell fields by as much as 84%, a magnitude of protection greater than reported for other CRF antagonists against other models of necrotic neuronal injury. Administration of astressin was done against both local microinfusion (0.035 μg) or systemic infusion (10 mg/kg body weight) of the excitotoxin; furthermore, the peptide protected even if administered only 10 min following excitotoxin exposure. This fulfills a critical prerequisite for any eventual therapeutic use of CRF antagonists, namely that they need not be administered in anticipation of a neurological insult.     

Extracellular signal-regulated kinase and c-Jun N-terminal protein kinase in ischemic tolerance.

The alterations and involvement of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal protein kinase (JNK) activation were examined in the hippocampal CA1 region in a rat model of global brain ischemic tolerance. Western blotting study showed that ERK activation (diphosphorylation) level was decreased (3.75-, 0.56-, and 0.23-fold vs sham control) and JNK activation level was increased (3.82-, 4.63-, and 5.30-fold vs sham control) 3 days after more severe ischemic insults (6 min, 8 min, and 10 min of ischemia, respectively). These alterations were significantly prevented by pretreatment with preconditioning ischemia, which also provided neuronal protection against ischemic injury. Inhibition of ERK activation after preconditioning ischemia by PD98059, a specific ERK kinase inhibitor, significantly prevented the inhibitory effects of preconditioning ischemia on both JNK activation and ischemic injury. The results suggest that ERK activation after preconditioning ischemia may result in the prevention of JNK activation and thus be involved in the protective responses in ischemic tolerance in hippocampal CA1 region.     

Hippocampal norepinephrine-like voltammetric responses following infusion of corticotropin-releasing factor into the locus coeruleus

Intracerebroventricular (i.c.v.) administration of corticotropin-releasing factor (CRF) increases the activity of noradrenergic neurons in the locus coeruleus (LC) assessed by electrophysiological and neurochemical studies. It has been suggested that this effect of i.c.v. CRF is exerted directly on LC noradrenergic (LC-NE) neurons. Infusion of CRF directly into the LC increases cortical and hippocampal release of norepinephrine (NE) as indicated by in vivo microdialysis studies, but the electrophysiological studies have shown both increases and decreases. The present study used in vivo voltammetry to study changes in the extracellular concentrations of NE in the rat hippocampus in response to infusion of CRF (100 ng) into the LC. When the infusion cannula was located in or very close to the LC, the immediate response to CRF was a small decrease in the NE-like oxidation current, followed by a robust increase after about 6-7 min. The oxidation current reached a peak around 13 min and returned to baseline by about 30 min after CRF infusion. By contrast with CRF, infusion of glutamate into the LC increased the oxidation current with a delay of around 30 s and a peak within 90 s. The responses to LC infusion of CRF in rats treated with DSP-4 to deplete hippocampal NE were substantially smaller than those in untreated rats, suggesting that the oxidation signals in untreated rats reflected changes in concentrations of NE. The response to glutamate was markedly augmented by pretreatment with the NE reuptake inhibitor, desmethylimipramine, suggesting that the observed responses reflected changes in NE. Infusion of the same dose of CRF into brain structures outside the LC did not elicit consistent changes in oxidation current in the hippocampus. The time course of the responses to CRF is compatible with previously reported electrophysiological responses of LC-NE neurons to CRF and with neurochemical evidence indicating that CRF can affect the activity of LC-NE neurons. The results indicate that CRF may act in or close to the LC to induce release of hippocampal NE, but the delayed response to CRF compared with that to glutamate, suggests that CRF does not directly activate LC-NE neurons.     

Hippocampal injury and neurobehavioral deficits are improved by PD 81,723 following hyperglycemic cerebral ischemia

We investigated the effects of PD 81,723, an allosteric enhancer for the adenosine A(1) receptor subtype, on hippocampal injury and Morris water maze (MWM) performance following hyperglycemic cerebral ischemia and reperfusion (4-VO, 10 min) in the rat. PD 81,723 (3 or 10 mg/kg) or the equivalent volume of saline was administered intraperitoneally 30 min prior to ischemia. Moderate hyperglycemia was achieved by administration of D-glucose (3g/kg, i.p.) 15 min prior to induction of ischemia. Morris water maze trials were performed on the 6th, 7th, and 8th days after the ischemic insult. The rat brains were sectioned (8 microm), stained with cresyl violet/acid fuchsin, and evaluated for hippocampal ischemic injury by an experimenter blinded to the treatment conditions. At the higher dose, PD 81,723 (10 mg/kg) had no effect on hippocampal injury or MWM performance following hyperglycemic ischemia compared to corresponding saline-treated animals. In contrast, a lower dose of PD 81,723 (3 mg/kg) resulted in significant (P < 0.05, n = 8) reduction of hippocampal injury following hyperglycemic ischemia. Furthermore, corresponding Morris water maze performance (latency, learning index, and cumulative distance swum) was significantly improved by PD 81,723 (P < 0.05, n = 8). The results of the present study suggest that, in the presence of PD 81,723, an A(1) allosteric enhancer, endogenously produced adenosine is sufficient to exert significant neuroprotection during hyperglycemic ischemia. Moreover, the present study provides further evidence for a neuromodulatory role of adenosine during hyperglycemic ischemia.     

Hippocampal noradrenergic responses to CRF injected into the locus coeruleus of unanesthetized rats

Intracerebral administration of corticotropin-releasing factor (CRF) activates cerebral noradrenergic neurons. Direct infusion of CRF into the locus coeruleus (LC) increases norepinephrine (NE) release in the cortex and hippocampus as assessed by in vivo microdialysis. In a recent study using in vivo chronoamperometry in anesthetized rats, CRF injected into the LC increased apparent NE release in the hippocampus, but did so after a significant delay, much longer than observed following infusion of glutamate into the same site. Because this delay may have been an artifact of the urethane anesthesia, we developed a method for chronoamperometric recording from the hippocampus of unanesthetized rats. CRF infusion into the LC of such animals induced an increase in the apparent release of hippocampal NE after a mean delay of about 7 min, reached a peak around 16 min after CRF, and dissipated within 30 min. Thus the response closely resembled that previously reported in urethane-anesthetized rats. As in anesthetized rats, glutamate infused into the same site resulted in a much more rapid response (starting within 1 min and with a peak around 7 min). These results suggest that the urethane anesthesia does not substantially alter hippocampal NE release following infusion of CRF into the LC, and that the relatively long delay in the response is not an artifact of the anesthesia. The large differences in the responses to glutamate and CRF suggest that the effects of CRF are not exerted directly on receptors on LC neurons, and more likely reflect indirect actions on other cells in this region.     

Control by tachykinin NK(2) receptors of CRF(1) receptor-mediated activation of hippocampal acetylcholine release in the rat and guinea-pig

In vivo microdialysis was employed to explore the effects of different selective non-peptides NK(1),NK(2) and NK(3) receptor antagonists on the corticotropin releasing factor (CRF)-induced release of acetylcholine (ACh) in the hippocampus of rats and guinea-pigs. In both species, the intracerebroventricular (i.c.v.) administration of CRF produced a time- and dose-dependent increase in hippocampal ACh release that was totally suppressed by an intraperitoneally (i.p.) pretreatment with the selective non-peptide CRF(1) receptor antagonist antalarmin (30 mg/kg). Pretreatment with the selective NK(2) receptor antagonist SR48968 (1mg/kg, i.p.) significantly reduced the increase of ACh induced by CRF. In contrast, its low-affinity enantiomer SR48965 (1mg/kg, i.p.) or the NK(1) receptor antagonist, GR205171 (1mg/kg, i.p.) did not exert any antagonist effect. Moreover, administration of the selective NK(3) receptor antagonist SR142801 (1mg/kg, i.p.) did not significantly reduce the CRF-induced hippocampal ACh release in guinea-pigs (the only species studied). The selective activity of SR48968 versus GR205171 or SR142801 indicates that NK(2) receptors play a major role in the control of CRF-induced hippocampal ACh release. Moreover, in freely moving rats, two sessions of stroking of the neck and back of the rat for 30 min, at 90 min intervals, known to be a stressful stimulus, produced a marked and reproducible increase in hippocampal ACh release. This effect was prevented by the administration of the two selective non-peptide CRF1 and NK(2) receptor antagonists antalarmin (30 mg/kg, i.p.) and SR48968 (1mg/kg, i.p.), respectively. This suggests that stress-induced activation of the hippocampal ACh system may be under the control of both endogenously released CRF and NKA, and opens the possibility of the existence of a functional interplay between the pathways containing these peptides as we observed in our experiments on anaesthetized animals.     

EGP-314 is expressed differentially in three brain zones at an early time in an experimentally induced ischemia rat model

Gene expression in frontal, occipital, and hippocampal regions of rat brains at 15 min of ischemic injury was studied in a rat model by producing focal cerebral ischemia through middle cerebral artery (MCA) occlusion without reperfusion. Catalase, epithelial glycoprotein (EGP-314), cytochrome C oxidase-subunit 1, ribosomal L31 protein, and ceruloplasmin were found to be differentially expressed. Specific primers were designed to study this newly reported brain EGP-314, a cellular adhesion molecule involved in cell-cell and cell-extracellular matrix interactions and related with cytoskeletal organization, differentiation, and proliferation. In the frontal and occipital lobes, EGP-314 expression was low in control and ischemic conditions and increased in sham injured conditions, whereas in the hippocampal region its expression was induced only by ischemia. In situ hybridization and immunohistochemistry revealed that EGP-314 mRNA and the protein were present in the ischemic hippocampus pyramidal neurons. DNA fragmentation was demonstrated by TUNEL and LM-PCR analysis in hippocampus region. TUNEL positive pyramidal neurons were observed at 15 min of ischemia. DNA ladder was found at 12 and 15 min of ischemia.     

Hypothermic treatment restores glucose regulated protein 78 (GRP78) expression in ischemic brain.

Mild hypothermia is a well-known method of reducing brain damage caused by traumatic, hypoxic, and ischemic injury. To elucidate the neuroprotective mechanism induced by hypothermic treatment, we compared gene expression profiles in the hippocampus of gerbils rendered ischemic for 15 min and then reperfused for 3 h under conditions of normothermia (37+/-0.5 degrees C) or hypothermic treatment (34+/-0.5 degrees C). Using the differential display method, we observed significantly reduced expression of the 78 kDa glucose regulated protein (GRP78), in ischemic gerbil hippocampus that underwent normothermic reperfusion, but normal GRP78 expression in animals that underwent hypothermic reperfusion. In situ hybridization and Northern blot analysis showed GRP78 mRNA expression was reduced in the CA1 region of the hippocampus under normothermic conditions, but was not reduced under hypothermic conditions. Western blot analysis also showed the levels of immunoreactive GRP78 protein decreased in neurons of the hippocampal CA-1 region under normothermia, but not under hypothermic treatments. Furthermore, adenovirus-mediated overexpression of GRP78 protects rat hippocampal neurons from cell death and inhibits the rise in intracellular calcium concentration normally induced by hydrogen peroxide. These results suggest that reduction in GRP78 expression contributes to cell damage in the ischemic brain and that hypothermia-mediated restoration of GRP78 expression is one mechanism that enhances neuronal survival.     

Selective vulnerability in the gerbil hippocampus following transient ischemia

Summary Following brief ischemia, the Mongolian gerbil is reported to develop unusual hippocampal cell injury (Brain Res 239:57–69, 1982). To further clarify this hippocampal vulnerability, gerbils were subjected to ischemia for 3, 5, 10, 20, and 30 min by bilateral occlusion of the common carotid arteries. They were perfusion-fixed after varying intervals of survival time ranging from 3 h up to 7 days. Following brief ischemia (5–10min), about 90% of the animals developed typical hippocampal damage. The lesion was present throughout the extent of the dorsal hippocampus, whereas damage outside the hippocampus was not observed. Each sector of the hippocampus showed different types of cell reaction to ischemia. Ischemic cell change was seen in scattered CA4 neurons, and reactive change was found in CA2, whereas CA1 pyramidal cells developed a strikingly slow cell death process. Ischemia for 3 min did not produce hippocampal lesion in most cases. Following prolonged ischemia (20–30min), brain injury had a wide variety in its extent and distribution. These results revealed that the gerbil brief ischemia model can serve as an excellent, reliable model to study the long-known hippocampal selective vulnerability to ischemia. Delayed neuronal death in CA1 pyramidal cells was confirmed after varying degrees of ischemic insult. These findings demonstrated that the pathology of neuronal injury following brief ischemia was by no means uniform nor simple.     

Neuroprotective Role of Exogenous Brain-Derived Neurotrophic Factor in Hypoxia–Hypoglycemia-Induced Hippocampal Neuron Injury via Regulating Trkb/MiR134 Signaling

Hypoxic–ischemic brain injury is an important cause of neonatal mortality and morbidity. Brain-derived neurotrophic factor (BDNF) has been reported to play a neuroprotective role in hypoxic–ischemic brain injury; however, the specific effects and mechanism of BDNF on hypoxic–hypoglycemic hippocampal neuron injury remains unknown. The current study investigated the action of BDNF in regulating cerebral hypoxic-ischemic injury by simulating hippocampal neuron ischemia and hypoxia. We found that BDNF, p-Trkb, and miR-134 expression levels decreased, and that exogenous BDNF increased survival and reduced apoptosis in hypoxic–hypoglycemic hippocampal neurons. The results also show that BDNF inhibits MiR-134 expression by activating the TrkB pathway. Transfection with TrkB siRNA and pre-miR-134 abrogated the neuroprotective role of BDNF in hypoxic–hypoglycemic hippocampal neurons. Our results suggest that exogenous BDNF alleviates hypoxic–ischemic brain injury through the Trkb/MiR-134 pathway. These findings may help to identify a potential therapeutic agent for the treatment of hypoxic–ischemic brain injury.     

Keratinocyte growth factor prevents ischemia-induced delayed neuronal death in the hippocampal CA1 field of the gerbil brain

Fibroblast growth factors (FGFs) are polypeptides with various biological activities in vivo and in vitro, and their receptors are expressed in the widespread and specific neuronal populations of the brain. In this study, we asked whether keratinocyte growth factor (KGF), one of the FGF superfamily, would express in the brain, and have neuroprotective against ischemic brain injury. In situ hybridization analysis revealed that intense silver grains for KGF mRNA are observed in the neuronal cells of the cerebral cortex, hippocampus and amygdala in gerbil brain. Continuous cerebroventricular infusion of KGF (20 microg) for a 7 day period to gerbils starting 2 days before temporary right carotid artery occlusion (20 min) resulted in a higher survival rate than seen in vehicle-treated ischemic animals. Subsequent histological examinations showed that KGF effectively prevented delayed neuronal death of the hippocampal CA1 region. In situ detection of DNA fragmentation (TUNEL staining) revealed that ischemic animals infused with KGF contained fewer TUNEL-positive neurons in the hippocampal CA1 field than those infused with vehicle alone at the forth and seventh day after ischemia. KGF-treated brain showed over-expression of KGF mRNA in the neuronal cells of the cerebral cortex, hippocampus only in the right hemisphere, which was the side of carotid artery occlusion, 8-10 h after ischemia. These findings suggest that KGF has a protective effect against ischemic hippocampal neuronal damage in vivo, which may provide a new therapeutic strategy in the survival and reconstruction of neurons in response to cerebral injury.     

Protection by rapid chemical preconditioning of stressed hippocampal slice: a study of cellular swelling using optical scatter imaging

It has been demonstrated that anoxic preconditioning protects against a subsequent 'lethal' injury in the hippocampal slice. The goal of this paper was to test the hypothesis that chemical preconditioning could help reduce the cellular swelling observed in excitotoxically injured hippocampal slices. The control slice was given a 10-min insult of 100 microM N-methyl-D-aspartate (NMDA) to simulate ischemic injury, followed by 30-min perfusion of standard Ringers solution. Cellular swelling was observed with a microscope designed to image light scatter changes resulting from cellular swelling. After the control NMDA injury, the average peak scatter change for CA1, CA3 and DG regions was 31.0 +/- 3.4, 22.4 +/- 4.8 and 27.6 +/- 4.6%, respectively. The peak scatter change of the overall slice was 26.0 +/- 3.6%. The experimental slices were preconditioned by three short 100 microM NMDA insults of 15 s each separated by 10 min of standard Ringers solution perfusion. The slices then received 10 min of 'lethal' injury by 100 microM NMDA. It was observed that the overall scatter signal, as a measure of cellular swelling, was reduced by 8.0% (P<0.05, n=11) after preconditioning. A regional heterogeneity in the responses was also observed. Cellular swelling in CA1, CA3 and DG were reduced by 9.8% (P<0.001, n=11), 9.2% (P<0.005, n=11) and 7.7% (P<0.05, n=11), respectively, when compared to the control. This study presents experimental evidence that short episodes of preconditioning may protect against acute cellular swelling under ischemic conditions.     

Intracerebroventricular infusion of CRF increases extracellular concentrations of norepinephrine in the hippocampus and cortex as determined by in vivo voltammetry

Previous studies have indicated that intracerebroventricular (i.c.v.) infusions of corticotropin-releasing factor (CRF) activate locus coeruleus (LC) noradrenergic neurons and increase the metabolism and extracellular concentrations of norepinephrine (NE) in several brain regions, suggesting increased release. To examine the temporal aspects and mechanism of the presumed release of NE, CRF was infused i.c.v. and the oxidation current was recorded using carbon fiber voltammetric electrodes placed in rat hippocampus or cortex. The CRF (1 μg, i.c.v.) caused a significant increase of oxidation current with a delay of approximately 5 min, and a peak at approximately 35 min. Similar responses were observed in the medial prefrontal cortex. The hippocampal response was markedly attenuated when CRF was infused into rats pretreated with DSP-4 to deplete NE, suggesting that the observed changes in current resulted from oxidation of NE. The increase of NE-like current did not occur when 25 μg alpha-helical CRF_9–41 (ahCRF) was injected immediately before 1 μg CRF, suggesting that the response was mediated by cerebral CRF-receptors. Subcutaneous pretreatment with the ganglionic blocker, chlorisondamine, at a dose of 3 mg/kg had no effect on the voltammetric response to CRF, but a 6 mg/kg dose completely prevented the response. The β-adrenoceptor antagonists, S-propranolol (5 mg/kg), nadolol (5 and 10 mg/kg), and timolol (5 mg/kg) attenuated the NE response to i.c.v. CRF to varying degrees. When chlorisondamine (3 μg) or nadolol (5 μg) were given i.c.v. before the CRF, the hippocampal responses were not blocked. These results suggest peripheral actions of ganglionic and β-adrenergic blockers. We conclude that peripheral autonomic mechanisms, and probably both central and peripheral β-adrenoceptors, contribute to the increased secretion of hippocampal NE in response to i.c.v. CRF.     

Optimized protocol to reduce variable outcomes for the bilateral common carotid artery occlusion model in mice

The pre-clinical global ischemia model transient bilateral common carotid artery occlusion addresses the unique cascade of events leading to delayed neuronal cell death. However, the inconsistent occurrence of posterior communicating arteries (PcomA) in mice might cause high outcome variability. To determine a means for reducing variability, CD1 mice were subjected to bilateral common carotid artery occlusion for 12-40 min. Occlusion duration> or =18 min was applied to mice with bilateral regional cerebral blood flow (rCBF)> or =10% of baseline at 2.5 min of ischemia. However, only groups with ischemic duration< or =18 min were used for statistical analysis because of the high mortality in the other groups. After 7 days, patency of PcomA and hippocampal neuronal loss in the CA1 subfield were evaluated. Outcome variability was reduced when hemispheres containing PcomA were excluded from analysis; ischemic outcome was not affected by the presence of a contralateral PcomA. Extending ischemic duration based on rCBF did not reduce outcome variability because the initial rCBF could not reliably predict PcomA. Therefore, after an optimal ischemic duration, evaluating hippocampal injury in each hemisphere independently according to the existence of PcomA is an effective and reliable method to obtain consistent results in this pre-clinical mouse model.     

A synthetic NCAM-derived peptide, FGL, protects hippocampal neurons from ischemic insult both in vitro and in vivo

There is a major unmet need for development of innovative strategies for neuroprotection against ischemic brain injury. Here we show that FGL, a neural cell adhesion molecule (NCAM)-derived peptide binding to and inducing phosphorylation of the fibroblast growth factor receptor (FGFR), acts neuroprotectively after an ischemic insult both in vitro and in vivo. The neuroprotective activity of FGL was tested in vitro on dissociated rat hippocampal neurons and hippocampal slice cultures, using a protocol of oxygen-glucose deprivation (OGD). FGL protected hippocampal neurons from damage and maintained or restored their metabolic and presynaptic activity, both if employed as a pretreatment alone to OGD, and if only applied after the insult. In vivo 24 h pretreatment with a single suboccipital injection of FGL significantly protected hippocampal CA1 neurons from death in a transient global ischemia model in the gerbil. We conclude that FGL promotes neuronal survival after ischemic brain injury.     

Neuronal mechanisms contribute to corticotropin-releasing factor-induced anti-oedema effect in the rat hind paw

The present study is designed to elucidate the involvement of neuronal mechanisms in corticotropin-releasing factor (CRF)-induced anti-oedema effects. Oedema was induced in the rat hind paw by subcutaneous injection of 3 nmol of serotonin (5-HT). A single dose of CRF (9.4, 37.5 or 75 pmol) was given either ipsilaterally or contralaterally 30 min before 5-HT injection and oedema formation was subsequently measured every 30 min for 5.5 h. Compared to saline pre-treatment CRF (37.5 pmol) reduced oedema formation for 3.5 h when given ipsilaterally, and at 1.5 h (9.33, 37.5 and 75 pmol) when injected contralaterally. Administration of CRF along with CRF receptor antagonist, alpha-helical CRF, abolished the anti-oedema effects of CRF. Sciatic nerve ligation on the injected side attenuated the ipsilateral CRF-induced anti-oedema effect when compared with saline pre-treatment and sham-operated rats. Ipsilateral pre-treatment with 37.5 pmol of CRF caused a reduction in hind paw temperature compared to treatment with saline. Results of the present study indicate that the nervous system contributes to CRF effects in 5-HT-induced oedema formation.     

Sexually Dimorphic Response of TRPM2 Inhibition Following Cardiac Arrest-Induced Global Cerebral Ischemia in Mice

Transient global cerebral ischemia due to cardiac arrest followed by resuscitation (CA/CPR) causes significant neurological damage in vulnerable neuron populations within the brain, such as hippocampal CA1 neurons. In recent years, we have implicated the transient receptor potential M2 (TRPM2) channel as a mediator of ischemic injury to neurons. We previously demonstrated that genetic and pharmacological strategies that reduce TRPM2 function preferentially protect male neurons in vitro and reduce infarct volume following experimental stroke. Due to the narrow therapeutic window for intervention following ischemic stroke, it is important to assess the role of TRPM2 in other models of cerebral ischemia. Therefore, this study utilized a modified mouse model of CA/CPR to mimic more accurately the clinical condition by maintaining body and head temperatures near the physiological range throughout. Here, we report that inhibition of TRPM2 activity with clotrimazole reduces hippocampal CA1 neuronal injury when administered 30 min after resuscitation from cardiac arrest. Consistent with our previous observations, neuroprotection was observed in male mice and no effect on injury was observed in the female. These findings provide further evidence for TRPM2 as a target for protection against cerebral ischemia in the male brain.     

Influence of corticotrophin releasing factor on neuronal cell death in vitro and in vivo

Several studies have demonstrated that antagonists of the corticotrophin releasing factor (CRF) receptor markedly inhibit experimentally induced excitotoxic, ischaemic and traumatic brain injury in the rat, and that CRF expression is elevated in response to experimentally induced stroke or traumatic brain injury. CRF is also induced by the pro-inflammatory cytokine interleukin 1 (IL-1), which participates in various forms of neurodegeneration. The aim of this study was to test the hypothesis that CRF is toxic directly in vivo or in vitro. In primary cultures of rat cortical neurons, exposure to CRF (10 pM-100 nM) for 24 h failed to cause cell death directly, or to modify the neurotoxic effects of N-methyl-D-aspartate (NMDA). Similarly, infusion of CRF (0.3-5 microg) into specific brain regions of the rat did not induce cell death and did not significantly alter the neuronal damage produced by infusion of excitatory amino acids. These data demonstrate that CRF is not directly neurotoxic, and suggest that either CRF mediates neuronal damage by indirect actions (e.g. on the vasculature) and/or that CRF is not the endogenous ligand which contributes to neurodegeneration through activation of CRF receptors.     

Mechanisms of the anti-ischemic effect of vagus nerve stimulation in the gerbil hippocampus

The neuroprotective mechanisms of cervical vagus nerve stimulation (VNS) in transient ischemia were investigated. Left VNS (0.4 mA, 40 Hz) was performed during 5 min ischemia in gerbils. About 50% of the hippocampal neurons were rescued from ischemic insult by VNS, and this effect was prevented by transection of the vagus nerve centrally to the site of cervical stimulation. VNS significantly attenuated both ischemia-induced glutamate release and transient increase of hippocampal blood flow during reperfusion. Hyperemia as well as excessive glutamate release after ischemia is regarded as an important factor in ischemic brain damage as it leads to generate considerable reactive oxygen species. Thus, VNS might protect neurons from ischemia-induced glutamate excitotoxicity and reperfusion injury via the afferent path-way of the vagus.