Ginkgo biloba extract (EGb 761) prevents the ischemic brain injury-induced decrease in parvalbumin expression

Ginkgo biloba extract (EGb 761) exerts a neuroprotective effect against ischemic brain injury through an anti-apoptotic mechanism. Parvalbumin is a calcium buffering protein that plays an important role in modulating intracellular calcium concentration and regulating apoptotic cell death. The aim of this study was to investigate whether EGb 761 affects parvalbumin expression in cerebral ischemic injury. Adult male Sprague-Dawley rats were treated with vehicle or EGb 761 (100 mg/kg) prior to middle cerebral artery occlusion (MCAO) and cerebral cortex tissues were collected 24 h after MCAO. A proteomic approach revealed a reduction in parvalbumin expression in the vehicle-treated animals, whereas EGb 761 pretreatment attenuates the ischemic injury-induced decrease in parvalbumin expression. RT-PCR and Western blot analyses clearly confirmed the fact that EGb 761 prevents the injury-induced decrease in parvalbumin. Moreover, the results of immunohistochemical staining showed that the number of parvalbumin-positive cells was lower in vehicle-treated animals than in sham-operated animals, and EGb 761 averted this decrease. Thus, these results suggest that the maintenance of parvalbumin expression is associated with the neuroprotective function of EGb 761 against neuronal damage induced by ischemia.     

Neuroprotection of paclitaxel against cerebral ischemia/reperfusion-induced brain injury through JNK3 signaling pathway

In this study, we investigated the neuroprotective effects of paclitaxel in transient cerebral ischemia and possible regulatory mechanism of these neuroprotection. Our data showed that paclitaxel can down-regulate the increased MLK3, JNK3, c-Jun, Bcl-2, and caspase-3 phosphorylation induced by ischemia injury. Cresyl violet staining and immunohistochemistry results demonstrated that paclitaxel had neuroprotective effect against ischemia/reperfusion-induced neuronal cell death. These results indicated that paclitaxel has neuroprotection in ischemic injury through JNK3 signaling pathway and provided a novel possible drug in therapeutics of brain ischemia.     

Neuroprotection of paclitaxel against cerebral ischemia/reperfusion-induced brain injury through JNK3 signaling pathway

In this study, we investigated the neuroprotective effects of paclitaxel in transient cerebral ischemia and possible regulatory mechanism of these neuroprotection. Our data showed that paclitaxel can down-regulate the increased MLK3, JNK3, c-Jun, Bcl-2, and caspase-3 phosphorylation induced by ischemia injury. Cresyl violet staining and immunohistochemistry results demonstrated that paclitaxel had neuroprotective effect against ischemia/reperfusion-induced neuronal cell death. These results indicated that paclitaxel has neuroprotection in ischemic injury through JNK3 signaling pathway and provided a novel possible drug in therapeutics of brain ischemia.     

Neuroprotective properties of marrow-isolated adult multilineage-inducible cells in rat hippocampus following global cerebral ischemia are enhanced when complexed to biomimetic microcarriers

Cell-based therapies for global cerebral ischemia represent promising approaches for neuronal damage prevention and tissue repair promotion. We examined the potential of marrow-isolated adult multilineage-inducible (MIAMI) cells, a homogeneous subpopulation of immature human mesenchymal stromal cell, injected into the hippocampus to prevent neuronal damage induced by global ischemia using rat organotypic hippocampal slices exposed to oxygen-glucose deprivation and rats subjected to asphyxial cardiac arrest. We next examined the value of combining fibronectin-coated biomimetic microcarriers (FN-BMMs) with epidermal growth factor (EGF)/basic fibroblast growth factor (bFGF) pre-treated MIAMI compared to EGF/bFGF pre-treated MIAMI cells alone, for their in vitro and in vivo neuroprotective capacity. Na?ve and EGF/bFGF pre-treated MIAMI cells significantly protected the Cornu Ammonis layer 1 (CA1) against ischemic death in hippocampal slices and increased CA1 survival in rats. MIAMI cells therapeutic value was significantly increased when delivering the cells complexed with FN-BMMs, probably by increasing stem cell survival and paracrine secretion of pro-survival and/or anti-inflammatory molecules as concluded from survival, differentiation and gene expression analysis. Four days after oxygen and glucose deprivation and asphyxial cardiac arrest, few transplanted cells administered alone survived in the brain whereas stem cell survival improved when injected complexed with FN-BMMs. Interestingly, a large fraction of the transplanted cells administered alone or in complexes expressed βIII-tubulin suggesting that partial neuronal transdifferentiation may be a contributing factor to the neuroprotective mechanism of MIAMI cells.     

Melatonin ameliorates neural function by promoting endogenous neurogenesis through the MT2 melatonin receptor in ischemic-stroke mice

Melatonin has many protective effects against ischemic stroke, but the underlying neuroprotective mechanisms are not fully understood. Our aim was to explore the relationship between melatonin's neuroprotective effects and activation of the MT2 melatonin receptor in a murine ischemic-stroke model. Male ICR mice were subjected to a transient middle cerebral ischemic/reperfusional injury, and melatonin (5 and 10 mg/kg, ip) was administrated once daily starting 2 h after ischemia. More than 80% of the mice died within 5 days after stroke without treatment. Melatonin treatment significantly improved the survival rates and neural functioning with modestly prolonged life span of the stroke mice by preserving blood-brain barrier (BBB) integrity via a reduction in the enormous amount of stroke-induced free radical production and significant gp91(phox) cell infiltration. These protective effects of melatonin were reversed by pretreatment with MT2 melatonin receptor antagonists (4-phenyl-2-propionamidotetralin (4P-PDOT) and luzindole). Moreover, treatment with melatonin after stroke dramatically enhanced endogenous neurogenesis (doublecortin positive) and cell proliferation (ki67 positive) in the peri-infarct regions. Most ki67-positive cells were nestin-positive and NG2-positive neural stem/progenitor cells that coexpressed two neurodevelopmental proteins (adam11 and adamts20) and the MT2 melatonin receptor. RT-PCR revealed that the gene expression levels of doublecortin, ki67, adamts20, and adam11 are markedly reduced by stroke, but are restored by melatonin treatment; furthermore, pretreatment with 4P-PDOT and luzindole antagonized melatonin's restorative effect. Our results support the hypothesis that melatonin is able to protect mice against stroke by activating MT2 melatonin receptors, which reduces oxidative/inflammatory stress. This results in the preservation of BBB integrity and enhances endogenous neurogenesis by upregulating neurodevelopmental gene/protein expression.     

Molecular mechanisms of neuroprotective action of immunosuppressants--facts and hypotheses

Cyclosporin A (CsA) and FK506 (Tacrolimus) are short polypeptides which block the activation of lymphocytes and other immune system cells. Immunosuppressants exert neuroprotective and neurotrophic action in traumatic brain injury, sciatic nerve injury, focal and global ischemia in animals. Their neuroprotective actions are not understood and many hypotheses have been formed to explain such effects. We discuss a role of drug target - calcineurin in neuroprotective action of immunosuppressants. Protein dephosphorylation by calcineurin plays an important role in neuronal signal transduction due to its ability to regulate the activity of ion channels, glutamate release, and synaptic plasticity. In vitro FK506 protects cortex neurons from NMDA-induced death, augments NOS phosphorylation inhibiting its activity and NO synthesis. However, in vivo experiments demonstrated that FK506 in neuroprotective doses did not block excitotoxic cell death nor did it alter NO production during ischemia/reperfusion. Tissue damage in ischemia is the result of a complex pathophysiological cascade, which comprises a variety of distinct pathological events. Resident non-neuronal brain cells respond rapidly to neuronal cell death and may have both deleterious and useful role in neuronal damage. There is increasing evidence that reactive gliosis and post-ischemic inflammation involving microglia contribute to ischemic damage. We have demonstrated that FK506 modulates hypertrophic/proliferative responses and proinflammatory cytokine expression in astrocytes and microglia in vitro and in focal transient brain ischemia. Our findings suggest that astrocytes and microglia are direct targets of FK506 and modulation of glial response and inflammation is a possible mechanism of FK506-mediated neuroprotection in ischemia.     

Melatonin reduces cerebral edema formation caused by transient forebrain ischemia in rats

Reduction of cerebral edema, an early symptom of ischemia, is one of the most important remedies for reducing subsequent chronic neural damage in stroke. Melatonin, a metabolite of tryptophan released from the pineal gland, has been found to be effective against neurotoxicity in vitro. The present study was aimed to demonstrate the effectiveness of melatonin in vivo in reducing ischemia-induced edema using magnetic resonance imaging (MRI). Rats were subjected to middle cerebral artery (MCA) occlusion/reperfusion surgery. Melatonin was administered twice (6.0 mg/kg, p.o.): just prior to 1 h MCA occlusion and 1 day after the surgery. T2-weighted multislice spin-echo images were acquired 1 day after the surgery. Increases in T2-weighted signals in ischemic sites of the brain were clearly observed after MCA occlusion. The signal increase was found mainly in the striatum and in the cerebral cortex in saline-treated control rats. In the melatonin-treated group, the total volume of cerebral edema was reduced by 45.3% compared to control group (P < 0.01). The protective effect of melatonin against cerebral edema was more clearly observed in the cerebral cortex (reduced by 56.1%, P < 0.01), while the reduction of edema volume in the striatum was weak (reduced by 23.0%). The present MRI study clearly demonstrated that melatonin is effective in reducing edema formation in ischemic animals in vivo, especially in the cerebral cortex. Melatonin may be highly useful in preventing cortical dysfunctions such as motor, sensory, memory, and psychological impairments.     

Inhibition of MMP-9 by a selective gelatinase inhibitor protects neurovasculature from embolic focal cerebral ischemia

ABSTRACT: BACKGROUND: Cerebral ischemia has been shown to induce activation of matrix metalloproteinases (MMPs), particularly MMP-9, which is associated with impairment of the neurovasculature, resulting in blood-brain barrier breakdown, hemorrhage and neurodegeneration. We previously reported that the thiirane inhibitor SB-3CT, which is selective for gelatinases (MMP-2 and 9), could antagonize neuronal apoptosis after transient focal cerebral ischemia. RESULTS: Here, we used a fibrin-rich clot to occlude the middle cerebral artery (MCA) and assessed the effects of SB-3CT on the neurovasculature. Results show that neurobehavioral deficits and infarct volumes induced by embolic ischemia are comparable to those induced by the filament-occluded transient MCA model. Confocal microscopy indicated embolus-blocked brain microvasculature and neuronal cell death. Post-ischemic SB-3CT treatment attenuated infarct volume, ameliorated neurobehavioral outcomes, and antagonized the increases in levels of proform and activated MMP-9. Embolic ischemia caused degradation of the neurovascular matrix component laminin and tight-junction protein ZO-1, contraction of pericytes, and loss of lectin-positive brain microvessels. Despite the presence of the embolus, SB-3CT mitigated these outcomes and reduced hemorrhagic volumes. Interestingly, SB-3CT treatment for seven days protected against neuronal laminin degradation and protected neurons from ischemic cell death. CONCLUSION: These results demonstrate considerable promise for the thiirane class of selective gelatinase inhibitors as potential therapeutic agents in stroke therapy.     

Post-treatment of Bax-inhibiting peptide reduces neuronal death and behavioral deficits following global cerebral ischemia

Cerebral ischemia is a major cause of adult disability and death worldwide. Evidence suggests that Bax-dependent initiation and activation of intrinsic apoptotic pathways contribute to ischemic brain injury. We investigated the Bax-inhibiting peptide VPALR, designed from the rat Ku70-Bax inhibiting domain, on the apoptotic neuronal cell death and behavioral deficits following global cerebral ischemia. The pentapeptide was infused into the left lateral ventricle of the rat brain by intracerebroventricular (i.c.v.) injection 1 h after cerebral ischemia, and results showed that it highly permeated hippocampal neurons and bound to Bax protein in vivo. Post-treatment with VPALR reduced the delayed neuronal damage by approximately 78% compared to the non-treated ischemic control and scrambled peptide-treated rats. TUNEL analysis revealed that VPALR markedly reduced the ischemia-induced increase in apoptotic neuronal death in rat hippocampal CA1 region. VPALR post-treatment also significantly attenuated Bax activation and its mitochondrial translocation as compared with scrambled peptide-treated animals. Concomitantly, Bax-inhibiting peptide-treated rats showed reduced cytochrome c release from mitochondria to cytosol and reduced caspase-3 activation in response to cerebral ischemia, indicating that activation of the intrinsic apoptotic pathway was reduced. Furthermore, Bax-inhibiting peptide improved spatial learning and memory performance in the Morris water maze, which was seriously affected by global cerebral ischemia. In conclusion, Bax inhibition by cell-permeable pentapeptides reduced apoptotic neuronal injury in the hippocampal CA1 region and behavioral deficits following global ischemia. These results suggest that Bax is a potential target for pharmacological neuroprotection and that Bax-inhibiting peptide may be a promising neuroprotective strategy for cerebral ischemia.     

Leptin protects hippocampal CA1 neurons against ischemic injury

Leptin is an adipose hormone with well characterized roles in regulating food intake and energy balance. A novel neuroprotective role for leptin has recently been discovered; however, the underlying mechanisms are not clearly defined. The purpose of this study was to determine whether leptin protects against delayed neuronal cell death in hippocampal CA1 following transient global cerebral ischemia in rats and to study the signaling mechanism responsible for the neuroprotective effects of leptin. Leptin receptor antagonist, protein kinase inhibitors and western blots were used to assess the molecular signaling events that were altered by leptin after ischemia. The results revealed that intracerebral ventricle infusion of leptin markedly increased the numbers of survival CA1 neurons in a dose-dependent manner. Infusion of a specific leptin antagonist 10 min prior to transient global ischemia abolished the pro-survival effects of leptin, indicating the essential role of leptin receptors in mediating this neuroprotection. Both the Akt and extracellular signal-related kinase 1/2 (ERK1/2) signaling pathways appear to play a critical role in leptin neuroprotection, as leptin infusion increased the phosphorylation of Akt and ERK1/2 in CA1. Furthermore, pharmacological inhibition of either pathway compromised the neuroprotective effects of leptin. Taken together, the results suggest that leptin protects against delayed ischemic neuronal death in the hippocampal CA1 by maintaining the pro-survival states of Akt and ERK1/2 MAPK signaling pathways.     

Melatonin Ameliorates Injury and Specific Responses of Ischemic Striatal Neurons in Rats

Studies have confirmed that middle cerebral artery occlusion (MCAO) causes striatal injury in which oxidative stress is involved in the pathological mechanism. Increasing evidence suggests that melatonin may have a neuroprotective effect on cerebral ischemic damage. This study aimed to examine the morphological changes of different striatal neuron types and the effect of melatonin on striatal injury by MCAO. The results showed that MCAO induced striatum-related dysfunctions of locomotion, coordination, and cognition, which were remarkably relieved with melatonin treatment. MCAO induced severe striatal neuronal apoptosis and loss, which was significantly decreased with melatonin treatment. Within the outer zone of the infarct, the number of Darpp-32+ projection neurons and the densities of dopamine-receptor-1 (D1)+ and dopamine-receptor-2 (D2)+ fibers were reduced; however, both parvalbumin (Parv)+ and choline acetyltransferase (ChAT)+ interneurons were not significantly decreased in number, and neuropeptide Y (NPY)+ and calretinin (Cr)+ interneurons were even increased. With melatonin treatment, the loss of projection neurons and characteristic responses of interneurons were notably attenuated. The present study demonstrates that the projection neurons are rather vulnerable to ischemic damage, whereas the interneurons display resistance and even hyperplasia against injury. In addition, melatonin alleviates striatal dysfunction, neuronal loss, and morphological transformation of interneurons resulting from cerebral ischemia.     

Trefoil Factor 3 as an Endocrine Neuroprotective Factor from the Liver in Experimental Cerebral Ischemia/Reperfusion Injury

Cerebral ischemia, while causing neuronal injury, can activate innate neuroprotective mechanisms, minimizing neuronal death. In this report, we demonstrate that experimental cerebral ischemia/reperfusion injury in the mouse causes upregulation of the secretory protein trefoil factor 3 (TFF3) in the hepatocyte in association with an increase in serum TFF3. Partial hepatectomy (~60% liver resection) immediately following cerebral injury significantly lowered the serum level of TFF3, suggesting a contribution of the liver to the elevation of serum TFF3. Compared to wild-type mice, TFF3^-/- mice exhibited a significantly higher activity of caspase 3 and level of cell death in the ischemic cerebral lesion, a larger fraction of cerebral infarcts, and a smaller fraction of the injured cerebral hemisphere, accompanied by severer forelimb motor deficits. Intravenous administration of recombinant TFF3 reversed changes in cerebral injury and forelimb motor function due to TFF3 deficiency. These observations suggest an endocrine neuroprotective mechanism involving TFF3 from the liver in experimental cerebral ischemia/reperfusion injury.     

Cell-cycle regulators are involved in transient cerebral ischemia induced neuronal apoptosis in female rats

Recent evidence indicates that cell-cycle regulating proteins are involved in apoptotic process in post-mitotic neurons. In this study, we examined cell-cycle regulators for G1/S cell-cycle progression after a transient focal cerebral ischemia induced by middle cerebral artery (MCA) occlusion. In the cerebral frontoparietal cortex, we observed a marked induction of Cyclin D1 (a coactivator of Cdks), and proliferating cell nuclear antigen (PCNA), together with upregulated Cdk kinase activities. This process is accompanied with multiple phosphorylation of retinoblastoma (Rb) protein at Cdk phosphorylation sites in neurons from the ischemic cortex. We further examined DNA synthesis by the incorporation of BrdU, a nucleotide analog that incorporates into newly synthesized DNA. Within 24-h of reperfusion after 60-min occlusion, substantial BrdU-positive neurons were observed in the ischemic cortex. Inhibition of Cdk4 activity during this ischemia/reperfusion is highly neuroprotective. These results suggest that ischemia/reperfusion cerebral damage induces signalings at the G1/S cell-cycle transition, and may constitute a critical step in the neuronal apoptotic pathway in ischemia/reperfusion induced neuronal damage.     

Transforming growth factor-beta: a neuroprotective factor in cerebral ischemia

Transforming growth factor-β (TGF-β) has diverse and multiple roles throughout the body. This review focuses on the evidence supporting its functions in the central nervous system, with a particular emphasis on its purported role in cerebral ischemia. Numerous studies have documented that TGF-β1 levels are enhanced in the brain following cerebral ischemia. As evidence that such an upregulation is beneficial, agonist studies have demonstrated that TGF-β1 reduces neuronal cell death and infarct size following middle cerebral artery occlusion (MCAO), while conversely, antagonist studies have shown increased neuronal cell death and infarct size after MCAO. These studies suggest that TGF-β1 has a neuroprotective role in cerebral ischemia. Recent work with adenoviral-mediated overexpression of TGF-β1 in vivo in mice has further implicated a neuroprotective role for TGF-β1 in cerebral ischemia, as evidenced by a reduction in neuronal cell death, infarct size, and neurological outcome. Additionally, numerous in vitro studies have documented the neuroprotective ability of TGF-β1 in neurons from a variety of species, including rats, mice, chicks, and humans. Of significant interest, TGF-β1 was shown to be protective against a wide variety of death-inducing agents/insults, including hypoxia/ischemia, glutamate excitotoxicity, β-amyloid, oxidative damage, and human immunodeficiency virus. The mechanism of TGF-β1-mediated neuroprotection remains to be resolved, but early evidence suggests that TGF-β1 regulates the expression and ratio of apoptotic (Bad) and antiapoptotic proteins (Bcl-2, Bcl-x₁), creating an environment favorable for cell survival of death-inducing insults. Taken as a whole, these results suggest that TGF-β1 is an important neuroprotective factor that can reduce damage from a wide-array of death-inducing agents/insults in vitro, as well as exert protection of the brain during cerebral ischemia. The authors’ research is supported by research grants (HD-28964 and AG-17186 to DWB) from the National Institutes of Health, NICHD, and NIA.     

Protective Effect of Oren-gedoku-to Against Induction of Neuronal Death by Transient Cerebral Ischemia in the C57BL/6 Mouse

We examined the neuroprotective effects of oren-gedoku-to (TJ15), a herbal medicine, after transient forebrain ischemia. Transient forebrain ischemia was induced by occlusion of both common carotid arteries for 15 min in C57BL/6 mice treated with TJ15. In the control ischemic group without TJ15 treatment, histologic examination of brain tissue collected seven days after reperfusion showed death of pyramidal cells in CA2-3 area of the hippocampus, unilaterally or bilaterally. In mice treated with oral TJ15 (845 mg/kg/day) for five weeks, the frequency of ischemic neuronal death was significantly lower. Immunohistochemistry for Cu/Zn-superoxide dismutase (Cu/Zn-SOD) showed strongly reactive astrocytes in the hippocampus of ischemic mice treated with TJ15. Damage to nerve cells by free radicals plays an important role in the induction of neuronal death by ischemia-reperfusion injury. Our results suggest that TJ15 protects against ischemic neuronal death by increasing the expression of Cu/Zn-SOD and suggest that oren-gedoku-to reduces the exposure of hippocampal neurons to oxidative stress.     

Anti-inflammatory Effect of Tanshinone I in Neuroprotection Against Cerebral Ischemia–Reperfusion Injury in the Gerbil Hippocampus

Tanshinone I (TsI) is an important lipophilic diterpene extracted from Danshen (Radix Salvia miltiorrhizae) and has been used in Asia for the treatment of cerebrovascular diseases such as ischemic stroke. In this study, we examined the neuroprotective effect of TsI against ischemic damage and its neuroprotective mechanism in the gerbil hippocampal CA1 region (CA1) induced by 5 min of transient global cerebral ischemia. Pre-treatment with TsI protected pyramidal neurons from ischemic damage in the stratum pyramidale (SP) of the CA1 after ischemia–reperfusion. The pre-treatment with TsI increased the immunoreactivities and protein levels of anti-inflammatory cytokines [interleukin (IL)-4 and IL-13] in the TsI-treated-sham-operated-groups compared with those in the vehicle-treated-sham-operated-groups; however, the treatment did not increase the immunoreactivities and protein levels of pro-inflammatory cytokines (IL-2 and tumor necrosis factor-α). On the other hand, in the TsI-treated-ischemia-operated-groups, the immunoreactivities and protein levels of all the cytokines were maintained in the SP of the CA1 after transient cerebral ischemia. In addition, we examined that IL-4 injection into the lateral ventricle did not protect pyramidal neurons from ischemic damage. In conclusion, these findings indicate that the pre-treatment with TsI can protect against ischemia-induced neuronal death in the CA1 via the increase or maintenance of endogenous inflammatory cytokines, and exogenous IL-4 does not protect against ischemic damage.     

The Involvement of Mitochondrial Biogenesis in Selenium Reduced Hyperglycemia-Aggravated Cerebral Ischemia Injury

Selenium has been shown to possess antioxidant and neuroprotective effects by modulating mitochondrial function and activating mitochondrial biogenesis. Our previous study has also suggested that selenium protected neurons against glutamate toxicity and hyperglycemia-induced damage by regulating mitochondrial fission and fusion. However, it is still not known whether the mitochondrial biogenesis is involved in selenium alleviating hyperglycemia-aggravated cerebral ischemia reperfusion (I/R) injury. The object of this study is to define whether selenium protects neurons against hyperglycemia-aggravated cerebral I/R injury by promoting mitochondrial biogenesis. In vitro oxygen deprivation plus high glucose model decreased cell viability, enhanced reactive oxygen species production, and meanwhile stimulated mitochondrial biogenesis signaling. Pretreated with selenium significantly decreased cell death and further activated the mitochondrial biogenesis signaling. In vivo 30 min of middle cerebral artery occlusion in the rats under hyperglycemic condition enhanced neurological deficits, enlarged infarct volume, exacerbated neuronal damage and oxidative stress compared with normoglycemic ischemic rats after 24 h reperfusion. Consistent to the in vitro results, selenium treatment alleviated ischemic damage in hyperglycemic ischemic animals. Furthermore, selenium reduced the structural changes of mitochondria caused by hyperglycemic ischemia and further promoted the mitochondrial biogenesis signaling. Selenium activates mitochondrial biogenesis signaling, protects mitochondrial structure integrity and ameliorates cerebral I/R injury in hyperglycemic rats.

     

Transient focal cerebral ischemia down-regulates glutamate transporters GLT-1 and EAAC1 expression in rat brain

Transient focal cerebral ischemia leads to extensive excitotoxic neuronal damage in rat cerebral cortex. Efficient reuptake of the released glutamate is essential for preventing glutamate receptor over-stimulation and neuronal death. Present study evaluated the expression of the glial (GLT-1 and GLAST) and neuronal (EAAC1) subtypes of glutamate transporters after transient middle cerebral artery occlusion (MCAO) induced focal cerebral ischemia in rats. Between 24h to 72h of reperfusion after transient MCAO, GLT-1 and EAAC1 protein levels decreased significantly (by 36% to 56%, p < 0.05) in the ipsilateral cortex compared with the contralateral cortex or sham control. GLT-1 and EAAC1 mRNA expression also decreased in the ipsilateral cortex of ischemic rats at both 24h and 72h of reperfusion, compared with the contralateral cortex or sham control. Glutamate transporter down-regulation may disrupt the normal clearance of the synaptically-released glutamate and may contribute to the ischemic neuronal death.     

Nitric Oxide Synthetase Activity in Cerebral Post-Ischemic Reperfusion and Effects of L-NG-Nitroarginine and 7-Nitroindazole on the Survival

Nitric Oxide (NO) mediates a series of physiological processes including regulation of vascular tone, macrophage-mediated cytotoxicity, platelet aggregation, learning and long-term potentiation, neuronal transmission. Although NO mediates several physiological functions, overproduction of NO can be detrimental and play multiple roles in the pathophysiology of focal cerebral ischemia. In the present study NOS activities were evaluated in cerebellum and cerebral cortex of ischemic and post-ischemic reperfused rats using an experimental model of partial cerebral ischemia; moreover, the effects of L-N^GNitroarginine (NA, nonselective NOS inhibitor) or 7-Nitroindazole (7-NI, selective neuronal NOS inhibitor) administration were assayed on percentage survival of ischemic rats. An increase of NOS activity in the cerebellum and in cerebral cortex of ischemic and post-ischemic reperfused rats was observed. NA administration failed to induce neuroprotective effects, by increasing percentage of mortality of treated ischemic rats with respect to control group. In contrast, the treatment with the selective neuronal NOS inhibitor, 7-NI, induced a significant neuroprotective effect.