Penumbra Zone Research Articles

Measurement of neuronal activity of individual neurons after stroke in the rat using a microwire electrode array

Background and purposeIschemic stroke induces spreading depression of brain waves and ischemic depolarizations, suggesting electrical activity of neurons is sensitive to stroke. The present study was designed to measure the electrophysiological response of an array of individual neurons to ischemic stroke in rats. MethodsA custom-made microwire electrode array (16 channels) was implanted in the cortical area supplied by the middle cerebral artery, spanning the core and boundary of the ischemic lesion. The electrophysiological activity of individual neurons was simultaneously recorded before, during and one week after middle cerebral artery occlusion (MCAo). ResultsNeuronal activities were significantly reduced immediately after MCAo. Intermittent silent periods (SP) appeared within minutes or hours after MCAo and lasted variable times. Between intermittent SP, neurons fired irregular bursting spikes (BS) with small magnitudes. Intermittent SP and irregular BS progressed in one day post stroke to persistent SP in channels close to the ischemic core or to regular BS with small amplitudes in the penumbral zone. Both persistent SP and regular BS persisted for at least seven days. ConclusionsElectrode array can be used to simultaneously record multiple individual neurons in response to ischemic stroke. This study provides the first evidence that the primary electrophysiological activity of multiple individual neurons to ischemic stroke is reduced in the lesion boundary and/or stopped in and adjacent to the lesion core.

Percutaneous Implantation of Cerebral Microdialysis Catheters by Twist-Drill Craniostomy in Neurocritical Patients: Description of the Technique and Results of a Feasibility Study in 97 Patients

Cerebral microdialysis is increasingly used to monitor several types of neurocritical patients. This study presents the technique used in our unit for percutaneous implantation of cerebral microdialysis catheters using a small twist-drill craniostomy that can be performed in the intensive care unit (ICU). We also present the results of this technique in 89 head-injured patients and in eight patients with a malignant middle cerebral artery (MCA) infarction. One hundred and twenty-two cerebral microdialysis catheters were implanted in the 97 patients included in this study. One cerebral microdialysis catheter was implanted in the less damaged hemisphere of 67 head-injured patients with a diffuse brain injury. An additional microdialysis catheter was inserted in the pericontusional parenchyma of 22 patients with brain contusions. In five of the eight patients with a malignant MCA infarction, only one microdialysis probe was inserted in the penumbral zone. In the remaining three patients, two cerebral microdialysis catheters were implanted in the same hemisphere (one in the ischemic core and the other in the penumbra). Technical problems were detected in 18 (15%) of the 122 microdialysis catheters implanted and were more frequent during the initial period of using microdialysis in our unit. In four patients (3% of implanted catheters), follow-up computed tomography (CT) scans showed a small intracerebral blood collection (always <or=1 cc) around the microdialysis catheter. There were no microdialysis-related infections. In conclusion, percutaneous insertion of single or multiple microdialysis catheters in neurocritical patients by using twist drill craniostomy is feasible, fast, and safe.

Cilostazol reduces ischemic brain damage partly by inducing metallothionein-1 and -2

The neuroprotective effect of cilostazol, an antiplatelet drug, was examined after 24 h permanent middle cerebral artery (MCA) occlusion in mice, and explored the possible underlying mechanism by examining metallothionein (MT)-1 and -2 induction in vivo. Cilostazol (30 mg/kg) was intraperitoneally administered at 12 h before, 1 h before, and just after MCA occlusion. Mice were euthanized at 24 h after the occlusion, and the neuronal damage was evaluated using 2,3,5-triphenyltetrazolium chloride (TTC) staining. Cilostazol significantly reduced the infarct area and volume, especially in the cortex. Real-time RT-PCR revealed increased mRNA expressions for MT-1 and -2 in the cortex of normal brains at 6 h after cilostazol treatment without MCA occlusion. MT-1 and -2 immunoreactivity was also increased in the cortex of such mice, and this immunoreactivity was observed in the ischemic hemisphere at 24 h after MCA occlusion (without cilostazol treatment). The strongest MT-1 and -2 immunoreactivity was detected in MCA-occlused mice treated with cilostazol [in the peri-infarct zone of the cortex (penumbral zone)]. These findings indicate that cilostazol has neuroprotective effects in vivo against permanent focal cerebral ischemia, especially in the penumbral zone in the cortex, and that MT-1 and -2 may be partly responsible for these neuroprotective effects.

Are Primary Supratentorial Intracerebral Hemorrhages Surrounded by a Biochemical Penumbra? A Microdialysis Study

Opinions vary regarding the indications for surgical evacuation of spontaneous intracerebral hemorrhages (ICH) and whether or not penumbra zones surround them. We performed intracerebral microdialysis (mean duration, 3.5 d) after surgical evacuation of ICH in 22 patients. Probes were placed in the parenchyma within 1 to 2 cm of the evacuated hematoma; a postoperative computed tomographic scanning verified their positions. The catheters were perfused with an artificial cerebrospinal fluid solution at 0.3 microl/min. Biochemical variables (glucose, pyruvate, lactate, glutamate, and glycerol) were analyzed and displayed at the bedside. The levels obtained were compared with previous data from normal human brains and the pericontusional penumbra zones of patients with severe traumatic brain lesions. During 1 to 12 hours after surgery, interstitial levels of glucose (median level, 1.3 mmol/L; interquartile range, 0.6-2.2 mmol/L) were within normal variations, whereas the levels of lactate (median level, 6.4 mmol/L; interquartile range, 3.9-9.0 mmol/L), glutamate (median level, 14 micromol/L; interquartile range, 5-370 micromol/L), and glycerol (median level, 190 micromol/L; interquartile range, 74-380 micromol/L), as well as the lactate/pyruvate ratio (median ratio, 35; interquartile range, 23-50) were increased. A gradual normalization of the lactate/pyruvate ratio and glycerol level was observed within 48 hours. The area close to an evacuated ICH exhibits a biochemical pattern similar to that of the biochemical penumbra zone surrounding focal traumatic brain contusions. The presence of a penumbra zone around large ICH may be of importance for making surgical decisions.

Origin sites of spontaneous cortical spreading depression migrated during focal cerebral ischemia in rats

Spontaneous cortical spreading depression (CSD) has been found to occur in the penumbral zone of the brain in rats with focal cerebral ischemia, and has been shown to promote expansion of infarction. Electrophysiological recording of CSD has been used for monitoring the penumbral zone, but with an inherently low spatial resolution; consequently, optical intrinsic signal imaging (OISI) was applied to characterize the spontaneous CSD waves following permanent left middle cerebral artery occlusion (MCAO) in rats under α-chloralose/urethane anesthesia. Besides the previous report about the regional variation of optical reflectance during spontaneous CSD following MCAO, the origin site of CSD was easily determined using OISI with the benefit of high resolution in the present study. Those origin points ( n = 82) were dynamically located in the ipsilateral hemisphere cortex: sometimes outside of the 6 mm × 8 mm observation area in the parietal cortex ( n = 19, 23%), and sometimes inside ( n = 63, 77%). The data showed a general trend towards the medial cortex (0.40 ± 0.15 mm per CSD). Because the lateral cortex of the rat brain proved to be infarcted with 2% 2,3,5-triphenyltetrazolium chloride (TTC) staining after 4 h occlusion, the migration of the origin sites implied a growth of the infarcted area. Hence, the determination of origins of spontaneous CSD using OISI would contribute to the continued study of stroke.

Temporal profile of ultrastructural changes in cortical neurons after a compression lesion

We studied the occurrence of apoptosis and secondary delayed cell death at various time points in the penumbra zone, which is the target for therapeutic intervention after stroke. A compression lesion was induced in the right sensory motor cortex of rat brains. At 0.5, 1, 3, 6, 12, 24, 48 and 72 h after lesioning, motor functions were evaluated by behavioral tests, and cortical layers IV and V were examined by electron microscopy. Behavioral recovery was observed at 48 h after lesioning. At 0.5-1 h in the lesioned area, the neuropil was expanded and contained affected cells. Apoptotic cells were found between 0.5-72 h, and at 12 h, 47.3 % of the total cell number was apoptotic cells. On the contralateral side, cells showed an enlarged endoplasmic reticulum at 3 h, indicating secondary delayed cell death. Our results show that a compression lesion is a useful model for studying ultrastructural changes in injured cells. The lesion results in the penumbra zone with apoptotic cell death between 0.5-72 h. As secondary delayed cell death occurred on the contralateral side at three hours after lesioning might be the time period during which injured, but still viable, neurons can be targets for acute treatment.

Noradrenergic Agonists and Antagonists Influence Migration of Cortical Spreading Depression in Rat—a Possible Mechanism of Migraine Prophylaxis and Prevention of Postischemic Neuronal Damage

Cortical spreading depression (CSD) is thought to be a neuronal mechanism that expands the penumbra zone after focal brain ischemia and that causes migraine aura. Both adrenergic agonists and antagonists significantly influence the size of the penumbra zone and decline the frequency of migraine. To study whether these compounds act by influencing CSD, we applied different drugs topically to an area of the exposed cortex of anesthetized adult rats and observed the migration of CSD-related DC potential deflections across the treated area. The adrenergic agonist norepinephrine (1 mmol/L) and the alpha(2)-agonist clonidine (0.56 mmol/L) blocked reversibly the migration of CSD. The beta-blocker propranolol (250 micromol/L to 1 mmol/L) dose-dependently diminished migration velocity or even blocked migration of CSD. The CSD blockade by the alpha(2)-antagonist yohimbine (1.75 mmol/L) was because of its action on inhibitory 5-HT(1A) receptors. None of the substances in the concentrations used had influence on regional cerebral blood flow or on systemic arterial blood pressure. The data suggest that the interference of these compounds with CSD may contribute to their beneficial therapeutic effect. The effect of beta-receptor antagonists in human migraine needs further exploration, since these drugs also work in migraine without aura.

Lack of antiapoptotic effects of antiplatelet drug, aspirin and clopidogrel, and antioxidant, MCI-186, against focal ischemic brain damage in rats

Objectives: This study evaluated the antiapoptotic effect of antiplatelet drugs, aspirin and clopidogrel, and the antioxidant drug, MCI-186, against focal cerebral ischemic rat brain damage.Methods: Cerebral ischemia was mechanically induced by 2-hour occlusion of the left middle cerebral artery (MCA) using an intraluminal filament followed by 24-hour reperfusion.Results: The cerebral infarct size was little affected by oral administration of 300 mg/kg aspirin, 30 mg/kg clopidogrel or 100 mg/kg MCI-186, but was significantly reduced by 30 mg/kg cilostazol. However, intravenous administration of 10 mg/kg MCI-186 suppressed the infarct size. DNA fragmentation observed in the cortical tissues corresponding to the penumbral zone was not suppressed by aspirin, clopidogrel or MCI-186, but was significantly suppressed by cilostazol. Increased phosphorylation of phosphatase and tensin homolog deleted from chromosome 10 (PTEN) and Bax protein, and decreased Akt/cyclic AMP response element binding protein (CREB) phosphorylation, including Bcl-2 protein in the vehicle-treated group were not affected by treatment with aspirin, clopidogrel and MCI-186, whereas those effects were reversed by cilostazol.Conclusion: Thus, it is suggested that antiplatelet drugs, aspirin and clopidogrel, and antioxidant drug, MCI-186, showed little antiapoptotic effect in contrast to cilostazol.

Long-Term in Vivo Investigation of Mouse Cerebral Microcirculation by Fluorescence Confocal Microscopy in the Area of Focal Ischemia

This study was designed to assess that mouse pial and cortical microcirculation can be monitored in the long term directly in the area of focal ischemia, using in vivo fluorescence microscopy. A closed cranial window was placed over the left parieto-occipital cortex of C57BL/6J mice. Local microcirculation was recorded in real time through the window using laser-scanning confocal fluorescence microscopy after intravenous injection of fluorescent erythrocytes and dextran. The basal velocity of erythrocytes through intraparenchymal capillaries was 0.53+/-0.30 mm/sec (n=121 capillaries in 10 mice). Two branches of the middle cerebral artery were topically cauterized through the window. Blood flow evaluated by laser-Doppler flowmetry in two distinct areas indicated the occurrence of an ischemic core (15.2%+/-5.9% of baseline for at least 2 h) and a penumbral zone. Magnetic resonance imaging and histology were used to characterize the ischemic area at 24 h after occlusion. The infarct volume was 7.3+/-3.2 mm(3) (n=6). Microcirculation was repeatedly videorecorded using fluorescence confocal microscopy over the next month. After the decrease following arterial occlusion, capillary erythrocyte velocity was significantly higher than baseline 1 week later, and attained 0.74+/-0.51 mm/sec (n=76 capillaries in six mice, P<0.005) after 1 month, while venous and capillary network remodeling was assessed, with a marked decrease in tortuosity. Immunohistochemistry revealed a zone of necrotic tissue into the infarct epicenter, with activated astrocytes at its border. Such long-term investigations in ischemic cortex brings new insight into the microcirculatory changes induced by focal ischemia and show the feasibility of long-term fluorescence studies in the mouse cortex.

Intracerebral microdialysis in severe brain trauma: the importance of catheter location

Intracerebral microdialysis has attracted increasing interest as a monitoring technique during neurological/neurosurgical intensive care. The purpose of this study was to compare cerebral energy metabolism, an indicator of secondary excitotoxic injury and cell membrane degradation close to focal traumatic lesions ("penumbra zones") and in remote and apparently intact brain regions of the ipsilateral and contralateral hemispheres. The study included 22 consecutive patients with a mean age 44 +/- 17 years and an estimated postresuscitation Glasgow Coma Scale motor score less than 5. Altogether 40 microdialysis catheters with radiopaque tips were inserted. Two catheters could not be localized on postoperative computerized tomography (CT) scans and were excluded from the analysis. The perfusates were analyzed at the patient's bedside for levels of glucose, pyruvate, lactate, glutamate, and glycerol with the aid of a CMA 600 Analyzer. The positions of eight (22%) of the 36 catheters were reclassified after a review of findings on CT scans. Except for pyruvate the values of all biochemical variables and the lactate/pyruvate (L/P) ratio were significantly different in the penumbra zone when compared with mean values found in "normal" tissue ipsilateral to the parenchymal damage and in contralateral normal tissue (p < 0.001). In the penumbra zone a slow normalization of the L/P ratio and levels of glutamate and glycerol were observed. In normal tissue these parameters remained within normal limits. Data obtained from intracerebral microdialysis can be correctly interpreted only if the locations of the catheters as they relate to focal brain lesions are visualized. A "biochemical penumbra zone" surrounds focal traumatic brain lesions. It remains to be proven whether therapeutic interventions can protect the penumbra zone from permanent damage.

Migration of Cortical Spreading Depression (CSD) in Adult Rats can be Inhibited by Norepinephrine, Clonidine, Yohimbine, and Propranolol

Spreading depression is thought to be a neuronal mechanism that expands the penumbra zone after focal brain ischemia. Furthermore, cortical spreading depression (CSD) is assumed to be a neuronal mechanism underlying migraine aura. Interestingly, the sizes of the penumbra after both focal ischemia and migraine are significantly influenced by adrenergic agonists and antagonists. In human migraine beta-adrenoreceptor blockers are efficiently used for prophylaxis. The particular action of these adrenergic drugs is unknown, but vascular effects are often discussed. Alternatively, it is conceivable that adrenergic compounds act on the neuronal events that are involved in the pathophysiology during ischemia and migraine. Indeed, propranolol efficiently blocked SD in a retinal preparation where no vessels were present. To study whether adrenergic agonists or antagonists influence CSD, we applied different drugs topically to an area of the exposed cortex of anaesthetized adult rats (sodium thiopental, 100mg/kg, i.p.) and observed the migration of CSD-related DC potential deflections with glass microelectrodes at cortical depths of 800 and 1200µm in front of and behind the treated area. The adrenergic agonists norepinephrine (1 mM) and clonidine (0.56 mM) blocked reversibly the migration of CSD. The beta-blocker propranolol (250µM to 1mM) dose-dependently diminished migration velocity or even blocked migration of CSD. The alpha2-antagonist yohimbine (1.75 mM) showed a similar effect as norepinephrine, probably via its affinity to inhibitory 5-HT1A receptors. None of the substances in the concentrations used had an influence on regional cerebral blood flow or on systemic arterial blood pressure. The results show that alpha2-agonists, and beta-adrenoceptor antagonists can inhibit the migration of CSD. Thus, the interference of these compounds with CSD may contribute to their beneficial effect. The effect of beta-receptor antagonists in human migraine needs further exploration, because only a subgroup of migraine patients suffers from migraine with aura and because CSD does not directly activate the trigeminal nociceptive system. Supported by IZKF Jena (IZKF B378–10102).

Neuroprotective effect of tacrolimus (FK506) on ischemic brain damage following permanent focal cerebral ischemia in the rat

We investigated the neuroprotective effect of tacrolimus (FK506) on the ischemic cell death with respect to cytochrome c translocation and DNA fragmentation, which are pivotal events in the necrotic and apoptotic signaling pathway, using permanent focal cerebral ischemia in rats. Immunohistochemically, cytochrome c was observed in the cytoplasm as early as 1 h after middle cerebral artery (MCA) occlusion in the infarcted hemisphere. Cytosolic release of cytochrome c after MCA occlusion was also confirmed by Western blot analysis and enzyme immunoassay. Terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL) showed DNA fragmentation evolving in the ipsilateral cortex and the caudate putamen after 3 and 6 h, respectively, following MCA occlusion. Tacrolimus (1 mg/kg, i.v.), administered immediately after MCA occlusion, significantly attenuated the release of cytochrome c in the ischemic region, the number of TUNEL-positive cells in the ischemic penumbra zone, and the size of cortical ischemic lesions. This study demonstrated that tacrolimus ameliorated the accumulation of cytochrome c in the cytosol and the increase of TUNEL-positive cells induced by cerebral ischemia, indicating that the neuroprotective action of tacrolimus on ischemic brain injury caused by permanent focal cerebral ischemia could partially be attributed to the attenuation of the activation of the apoptotic execution machinery.

Transplantation of gene-transfected neural stem cells for transient cerebral ischemia in rats

To detect the expression and the role of vascular endothelial growth factor (VEGF)-transfected neural stem cells (NSCs) in rat brain subjected to ischemia. Fetal NSCs were cultured from E14 days SD rats and transfected with VEGF121 gene by using lipofectAMINE technique. The gene expression of transfected cells was detected by RT-PCR and immunofluorescent staining in vitro. Temporary middle cerebral artery occlusion (tMCAO) model was established in 40 SD rats and then rate were randomly divided into (1) control group (n = 10), (2) PBS transplantation group (n = 10), (3) neural stem cells transplantation group (n = 10), and (4) VEGF-secreting neural stem cells transplantation group (n = 10). BrdU-labelled NSCs and VEGF-secreting NSCs were transplanted into the penumbra zones respectively 3 days after the tMCAO model was established. Neurological Severity Score (NSS) was checked in all groups 2, 4, 6, 8, 10, 12 weeks respectively after transplantation. One and 12 weeks after the transplantation, 10 rats in the group (4) were killed and then brains taken out respectively. By using immunofluorescent staining, the VEGF expression of transplanted cells 1 week after transplantation, differentiation and migration of transplanted neural stem cells 12 week after transplantation were detected respectively. VEGF-transfected neural stem cells could continuously express gene products during the first 2 weeks. Both transfected NSCs and their progeny expressed VEGF gene products, which was demonstrated by fluorescence study. There were no significant differences in NSS in groups 4 when tMCAO models were just established. However, the values of NSS in (4) group were 5.8 +/- 1.5, 5.0 +/- 1.0, 4.6 +/- 1.0, 4.0 +/- 0.7, 4.0 +/- 1.0, 3.8 +/- 0.4 from 2 approximately 12 weeks after transplantation, significantly lower than those in groups (1) and (2) 8 weeks (P = 0.008) and those in groups (1), (2) and (3) 12 weeks (P = 0.000) after transplantation. NSS in group (3) was also lower than that in groups (1) and (2) 8 and 12 weeks after transplantation. One week after transplantation, immunofluorescent staining showed that VEGF-transfected NSCs migrated and expressed VEGF into hosts' brains. Twelve weeks after transplantation, transplanted NSCs survived and migrated, some of them differentiated to neurons and integrated well with hosts' cytoarchitectural components. VEGF-transfected NSCs express gene products during the early time after transplantation, which reduce brain injury through protecting the vascular system against ischemia and reperfusion injury. Transplantation of VEGF-transfected NSCs might be a novel method for treatment of cerebral ischemia.

Lume di Lume: A Theory of Light and Its Effects

This article is an investigation of an enigmatic drawing from an Italian Renaissance treatise and its companion text. Its aim is to understand the drawing by situating it amid contemporary optical theory and to show how the text contributes a new appreciation for light in architecture in its time. Finally, it attempts to provide an interpretation of the drawing and text useful today — namely, the idea that architecture becomes visible not simply by its existence in light but in the creation of a penumbral zone between darkness and light.

Bcl-2 and Bax proteins are increased in neocortical but not in thalamic apoptosis following devascularizing lesion of the cerebral cortex in the rat: an immunohistochemical study

The hypothesis that devascularization of somatosensory and motor cortex causes apoptosis in infarcted regions and in the linked thalamic nuclei was evaluated. To unravel whether Bcl-related proteins, known to regulate apoptosis, participate in neuronal and glial responses to devascularization, we analyzed immunohistochemically the distribution and intensity of staining of Bcl-2 and Bax proteins at different time points after lesion. Both early (up to 6 h) and late (1–7 days) responses were studied. Devascularization led to rapid (within hours) apoptosis in the cortex and to a delayed (within 3–7 days) apoptosis in thalamic nuclei. In control groups, Bcl-2 and Bax immunoreactivity (IR) was detected in neurons and oligodendrocytes but not in astrocytes or microglia. Following devascularization, Bcl-2 IR and Bax IR increased in neurons before the onset of the apoptosis. In the ischemic focus, the increase reached maximal values 3 h after the lesion. The increase was of slower onset in the penumbra zone (24 h and after), a region in which both proteins were induced in astrocytes also. The change of Bax IR intensity exceeded four times that of Bcl-2 at all time points investigated, indicating a diminution of Bcl-2/Bax ratio that may direct neurons to apoptotic pathway. In numerous neurons, an increase of IR in the cytoplasm was accompanied by induction of nuclear staining. No changes of Bcl-2 and Bax IR were found in thalamic nuclei. Our results point to different mechanisms underlying apoptosis of cortical and thalamic neurons. Nuclear appearance of Bcl-2 and Bax suggests they possess regulatory role of gene expression changes triggered by cortical infarct.

Assessment of critical thresholds for cerebral perfusion pressure by performing bedside monitoring of cerebral energy metabolism.

An intractable increase in intracranial pressure (ICP) leading to a progressive decrease in cerebral perfusion pressure (CPP) and cerebral blood flow (CBF) is the dominating cause of death in patients with severe brain trauma. Arterial hypotension may further compromise CPP (and CBF) and significantly contributes to death. In addition, the injured brain is sensitive to raised CPP due to an increased permeability of the blood-brain barrier (BBB) to crystalloids and an impaired pressure autoregulation of the CBF. Given these circumstances, an increase in CPP will cause a net transport of water across the BBB and a further elevation in ICP. Accordingly, the assessment of the lower critical threshold for CPP is important for neurological intensive care. This level varies among different patients and different areas of the brain. In fact, the penumbral zones surrounding focal brain lesions appear to be the most sensitive. In the individual patient, preservation of normal cerebral energy metabolism within areas at risk during a decrease in CPP can be guaranteed by performing intracerebral microdialysis and bedside biochemical analyses.

Cilostazol prevents focal cerebral ischemic injury by enhancing casein kinase 2 phosphorylation and suppression of phosphatase and tensin homolog deleted from chromosome 10 phosphorylation in rats.

This study shows the in vivo neuroprotective effect of cilostazol against cerebral ischemic injury evoked by subjecting rats to 2-h occlusion of middle cerebral artery (MCAO) followed by 24-h reperfusion. We observed the signaling pathway by which cilostazol suppressed MCAO-induced increased phosphorylation of phosphatase and tensin homolog deleted from chromosome 10 (PTEN) and apoptosis via increased phosphorylation of casein kinase 2 (CK2). When rats received 30 mg/kg cilostazol orally two times at 5 min and 4 h after the completion of ischemia, the infarct area was significantly reduced in the cortex and striatum with improvement of neurological deterioration. Increased DNA fragmentation in the penumbral zone was significantly reduced by cilostazol. Cilostazol significantly elevated phosphorylation levels of CK2, Akt, and cyclic AMP response element-binding protein (CREB) in association with increased Bcl-2 in the ischemic area, whereas the elevated PTEN phosphorylation was significantly reduced, all of which were antagonized by iberiotoxin, a maxi-K channel blocker, administered intracisternally 30 min before ischemia. In conclusion, cilostazol ameliorates the neuronal damage by suppression of apoptotic cell death via the maxi-K channel opening-coupled up-regulation of CK2 phosphorylation and down-regulation of PTEN phosphorylation with resultant increase in the Akt and CREB phosphorylation and increased Bcl-2 protein.

Evidence for a protective role played by the Na +/Ca 2+ exchanger in cerebral ischemia induced by middle cerebral artery occlusion in male rats

In the present paper, the role played by Na +/Ca 2+ exchanger (NCX) in focal cerebral ischemia was investigated. To this aim, permanent middle cerebral artery occlusion (pMCAO) was performed in male rats. The effects on the infarct volume of some inhibitors, such as tyrosine-6 glycosylated form of the exchanger inhibitory peptide (GLU-XIP), benzamil derivative (CB-DMB) and diarylaminopropylamine derivative (bepridil), and of the NCX activator, FeCl 3, were examined. FeCl 3, CB-DMB, bepridil and GLU-XIP, a modified peptide synthesized in our laboratory in order to facilitate its entrance into the cells through the glucose transporter, were intracerebroventricularly (icv) infused. FeCl 3 (10 μg/kg) was able to reduce the extenson of brain infarct volume. This effect was counteracted by the concomitant icv administration of CB-DMB (120 μg/kg). All NCX inhibitors, GLU-XIP, CB-DMB and bepridil, caused a worsening of the brain infarct lesion. These results suggest that a stimulation of NCX activity may help neurons and glial cells that are not irreversibly damaged in the penumbral zone to survive, whereas its pharmacological blockade can compromise their survival.

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L-arginine in focal cerebral ischemia

Nitric oxide and its precursor, L-arginine, have a great importance in cerebrovascular studies. In this study, we elucidate the dose dependent L-arginine effects on cerebral ischemia. The study involved 96 New Zealand albino rabbits, which were randomly allocated into four groups. The middle cerebral artery was occluded after a modified transorbital approach. Before the occlusion of MCA, each group was intravenously administered three doses of L-arginine i.e. 2.5 mg kg-1 for Group 1, 7.5 mg kg-1 for Group 2, and 12.5 mg kg-1 for Group 3. Thus, each group consisting of 24 animals was listed as 2.5 mg kg-1 (Group 1), 7.5 mg kg-1 (Group 2), 12.5 mg kg-1 (Group 3), and control group (receiving no intervention). Cerebral tissue oxygenization was measured in parietal area by near infrared spectroscopy in all animals prior to and at 5, 30, and 60 min after MCA occlusion. Six hours after MCA occlusion, all the animals were studied for the area of ischemia (n = 40), edema formation (n = 32), and blood nitrite-nitrate levels (n = 24). At the dose of 2.5 mg kg-1 of L-arginine no differences were detected on ischemic tissue volume, brain edema, cerebral tissue oxygenization, blood nitrite-nitrate levels when compared to the values of control group. However, with the dose of 7.5 mg kg-1, there were significant improvements in the levels of ischemic tissue volume, brain edema, and nitrite-nitrate levels compared to those of the control group and the 2.5 mg kg-1 group. At a dose of 12.5 mg kg-1, there were further improvements in the levels of ischemic tissue volume, brain edema, penumbral zone nitrite-nitrate levels. After 30 min of occlusion, cerebral tissue oxygenization values increased in a dose dependent fashion. L-arginine's protective effect on cerebrovascular ischemia shows a dose dependent effect on infract size and tissue water content that may prove beneficial in the treatment of ischemia. However, further dose-dependent studies are needed.