Stage Of Focal Cerebral Ischemia Research Articles

Neuroprotective nature of adipokine resistin in the early stages of focal cerebral ischemia in a stroke mouse model

New evidence suggests that resistin may have a therapeutic potential effect in management of neurodegenerative disease; but its role in the pathophysiology of stroke-induced injuries is not understood. However, further investigations are required to elucidate the effect of resistin and explore its possible molecular mechanisms on the ischemic reperfusion injury. Transient focal cerebral ischemia was induced by the middle cerebral artery occlusion (MCAO) in mice. Animal treated with resistin at doses of 25, 50, 100, 200, and 400 ng/mouse, on the MCAO commencement. Neurological function, infarct size, brain edema and Blood-brain barrier (BBB) disruption were measured. Additionally, content of malondialdehyde (MDA), TUNEL-positive cells and apoptosis-related proteins were assessed by immunohistochemistry and western blot techniques. Resistin mRNA was detected at 3 h, 6 h, 12 h and 24 h after MCAO using real-time QRT-PCR method. Central administration of resistin only at doses of 200 and 400 ng/mouse considerably reduced the infarct size and promoted neurological function (p < 0.001). In addition, resistin (400 ng/mouse) significantly decreased brain edema (p < 0.001), evans blue (EB) leakage (p < 0.05), MDA content (p < 0.005), apoptotic cells and apoptosis-related proteins (p < 0.001). Resistin mRNA expression markedly increased at 12-h time point and then returned to basal level at 24 h after MCAO. Our findings revealed that treatment with resistin could attenuate ischemic damage in a dose-dependent approach via suppressing apoptosis and oxidative stress. Application of resistin in clinical settings to treat stroke and brain ischemia warrants further research.

Blood -brain barrier disruption was less under isoflurane than pentobarbital anesthesia via a PI3K/Akt pathway in early cerebral ischemia.

One of the important factors altering the degree of blood-brain barrier (BBB) disruption in cerebral ischemia is the anesthetic used. The phosphoinositide 3-kinase (PI3K)/Akt signaling pathway has been reported to be involved in modulating BBB permeability and in isoflurane induced neuroprotection. This study was performed to compare the degree of BBB disruption in focal cerebral ischemia under isoflurane vs pentobarbital anesthesia and to determine whether inhibition of PI3K/Akt would affect the disruption in the early stage of focal cerebral ischemia. Permanent middle cerebral artery (MCA) occlusion was performed in rats under 1.4% isoflurane or pentobarbital (50mg/kg i.p.) anesthesia with controlled ventilation. In half of each group LY294002, which is a PI3K/Akt inhibitor, was applied on the ischemic cortex immediately after MCA occlusion. After one hour of MCA occlusion, the transfer coefficient (Ki) of 14C-α-aminoisobutyric acid (14C-AIB) was determined to quantify the degree of BBB disruption. MCA occlusion increased the Ki both in the isoflurane and pentobarbital anesthetized rats. However, the value of Ki was lower under isoflurane (11.5±6.0μL/g/min) than under pentobarbital (18.3±7.1μL/g/min) anesthesia. The Ki of the contralateral cortex of the pentobarbital group was higher (+74%) than that of the isoflurane group. Application of LY294002 on the ischemic cortex increased the Ki (+99%) only in the isoflurane group. The degree of BBB disruption by MCA occlusion was significantly lower under isoflurane than pentobarbital anesthesia in the early stage of cerebral ischemia. Our data demonstrated the importance of choice of anesthetics and suggest that PI3K/Akt signaling pathway plays a significant role in altering BBB disruption in cerebral ischemia during isoflurane but not during pentobarbital anesthesia.

Comparison of USPIO-enhanced MRI and Gd-DTPA enhancement during the subacute stage of focal cerebral ischemia in rats

Being one class of magnetic resonance imaging (MRI) contrast agents, ultrasmall superparamagnetic particles of iron oxides (USPIO) bear the potential to study neuroinflammation following stroke, but there is still debate over whether the iron oxides particles may enter the brain tissue passively over a damaged blood-brain barrier (BBB). To compare the enhancement patterns of USPIO and gadopentate dimeglumine (Gd-DTPA) during the subacute stage of focal cerebral ischemia, to examine the relationship between USPIO enhancement and BBB disturbance, as well as with neuroinflammatory cell response. Multiple MR sequences were obtained on days 3 and 6 after transient middle cerebral artery occlusion induced in rats with and without the application of USPIO and Gd-DTPA. The enhancement patterns of the two contrast agents were compared and correlated to histology, including IgG for BBB permeability, Prussian Blue staining for iron particle detection, and CD68 immunohistochemistry staining to identify macrophage/microglia. Gd-DTPA enhancement depicted BBB breakdown being in line with IgG leakage. The USPIO enhanced images demonstrated both diffuse and focal signal alteration in ischemic lesions. The diffuse enhanced pattern had a similar spatial and temporal profile as with Gd-DTPA enhancement. In addition, focal enhanced signal loss was visible on T1-, T2-, and T2*-weighted images, with a peak tendency of MR signal loss, macrophage/microglia concentration and iron particle accumulation at a later phase of the study. After focal cerebral ischemia, Gd-DTPA-enhanced MRI showed a higher sensitivity in detecting BBB alterations than did USPIO enhancement. USPIO provided complementary information regarding inflammatory cell activity in neuroinflammatory to cerebral ischemia that had not been visualized using conventional Gd-DTPA. The assessment using multiple MR parameters may identify intracellular and extracellular USPIO in vivo.

Human umbilical cord blood mesenchymal stem cell transplantation suppresses inflammatory responses and neuronal apoptosis during early stage of focal cerebral ischemia in rabbits.

Human umbilical cord blood mesenchymal stem cells (hUCB-MSCs) have been shown to ameliorate cerebral ischemia in animal models. In this study we investigated the effects of hUCB-MSCs on inflammatory responses and neuronal apoptosis during the early stage of focal cerebral ischemia in rabbits. Focal cerebral ischemia was induced in male New Zealand rabbits by occlusion of MCA for 2 h. The blood samples were collected at different time points prior and during MCAO-reperfusion. The animals were euthanized 3 d after MCAO, and the protein levels of IL-1β, IL-6, IL-10 and TNF-α in the serum and peri-ischemic brain tissues were detected using Western blot and ELISA, respectively. Inflammatory cell infiltration, neuronal apoptosis and neuronal density were measured morphologically. hUCB-MSCs (5 × 10(6)) were iv injected a few minutes after MCAO. The serum levels of IL-1β, IL-6 and TNF-α were rapidly increased, and peaked at 2 h after the start of MCAO. hUCB-MSC transplantation markedly and progressively suppressed the ischemia-induced increases of serum IL-1β, IL-6 and TNF-α levels within 6 h MCAO-reperfusion. Focal cerebral ischemia decreased the serum level of IL-10, which was prevented by hUCB-MSC transplantation. The expression of IL-1β, IL-6, IL-10 and TNF-α in the peri-ischemic brain tissues showed similar changes as in the serum. hUCB-MSC transplantation markedly suppressed the infiltration of inflammatory cells, and increased the neuronal density around the ischemic region. Furthermore, hUCB-MSC transplantation significantly decreased the percentage of apoptosis around the ischemic region. hUCB-MSCs transplantation suppresses inflammatory responses and neuronal apoptosis during the early stage focal cerebral ischemia in rabbits.

Effects of the Thioredoxin-1 Inhibitor PX-12 on Blood-Brain Barrier Permeability in the Early Stage of Focal Cerebral Ischemia

Background/Aims: Since a thioredoxin-1 (Trx-1) inhibitor, 1-methylpropyl-2-imidazolyl disulfide (PX-12) which is an antitumor agent, significantly decreased vascular permeability in tumor xenografts within a few hours of treatment, we tested whether PX-12 would attenuate blood-brain barrier (BBB) disruption in the early stage of focal cerebral ischemia and whether its action could be affected by vascular endothelial growth factor (VEGF) which interacts with the Trx-1 system. Methods: In rats, 40 min after intravenous infusion of either 25 mg/kg of PX-12 (PX-12 group) or normal saline (control group), a middle cerebral artery (MCA) was occluded. In half of each group, VEGF (10^-10 mol/l) was applied topically in the ischemic cortex (IC). Ninety minutes after MCA occlusion, the transfer coefficient (K_i) of ¹⁴C-α-aminoisobutyric acid and the volume of ³H-dextran distribution were determined to measure the degree of BBB disruption. VEGF protein levels were determined using Western blot analysis. Results: MCA occlusion increased the K_i in the control (+196%) as well as in the PX-12-treated rats (+90%), but the K_i of the IC of the PX-12 group was lower (-42%) than that of the control rats. VEGF protein levels were decreased in both the IC (-9.5%) and the contralateral cortex (CC; -10.2%) with PX-12 treatment. In the VEGF-treated rats, PX-12 also attenuated (-41%) the K_i of the IC. The difference in the volume of dextran distribution between the IC and the CC became insignificant with PX-12 treatment with or without VEGF application. Conclusion: Our data demonstrated that PX-12 was effective in decreasing BBB disruption in the early stage of focal cerebral ischemia and that VEGF is not an important factor involved in the action of PX-12 on BBB permeability.

Green tea polyphenols alleviate early BBB damage during experimental focal cerebral ischemia through regulating tight junctions and PKCalpha signaling

BackgroundIt has been supposed that green tea polyphenols (GTPs) have neuroprotective effects on brain damage after brain ischemia in animal experiments. Little is known regarding GTPs’ protective effects against the blood-brain barrier (BBB) disruption after ischemic stroke. We investigated the effects of GTPs on the expression of claudin-5, occludin, and ZO-1, and the corresponding cellular mechanisms involved in the early stage of cerebral ischemia.MethodsMale Wistar rats were subjected to a middle cerebral artery occlusion (MCAO) for 0, 30, 60, and 120 min. GTPs (400 mg/kg/day) or vehicle was administered by intragastric gavage twice a day for 30 days prior to MCAO. At different time points, the expression of claudin-5, occludin, ZO-1, and PKCα signaling pathway in microvessel fragments of cerebral ischemic tissue were evaluated.ResultsGTPs reduced BBB permeability at 60 min and 120 min after ischemia as compared with the vehicle group. Transmission electron microscopy also revealed that GTPs could reverse the opening of tight junction (TJ) barrier at 60 min and 120 min after MACO. The decreased mRNA and protein expression levels of claudin-5, occludin, and ZO-1 in microvessel fragments of cerebral ischemic tissue were significantly prevented by treatment with GTPs at the same time points after ischemia in rats. Furthermore, GTPs could attenuate the increase in the expression levels of PKCα mRNA and protein caused by cerebral ischemia.ConclusionsThese results demonstrate that GTPs may act as a potential neuroprotective agent against BBB damage at the early stage of focal cerebral ischemia through the regulation of TJ and PKCα signaling.

The Effects of Isoflurane Pretreatment on Cerebral Blood Flow, Capillary Permeability, and Oxygen Consumption in Focal Cerebral Ischemia in Rats

We performed experiments to test whether isoflurane pretreatment produces vascular effects, especially at the levels of arterioles and capillaries affecting regional cerebral blood flow (rCBF), O(2) supply and consumption, or capillary permeability in focal cerebral ischemia. Because inducible nitric oxide synthase (iNOS) was implicated as one of the mechanisms of isoflurane preconditioning, the effect of iNOS inhibition on rCBF was also studied. Twenty-four hours before middle cerebral artery (MCA) occlusion, rats were pretreated with 2% isoflurane for 30 minutes using an endotracheal tube and mechanical ventilation for the isoflurane preconditioned (IsoPC) group. For the group of iNOS inhibition, aminoguanidine 200 mg/kg was injected IP 30 minutes before isoflurane pretreatment. One hour after MCA occlusion, rCBF was measured using (14)C-iodoantipyrine autoradiography. Alternate slices of the tissue were used to determine arteriolar and venular O(2) saturation using cryo microspectrophotometry. Capillary permeability was determined by measuring the transfer coefficient (Ki) of (14)C-alpha-aminoisobutyric acid. Additional measurements of rCBF were performed at 3 hours after MCA occlusion. MCA occlusion decreased rCBF and O(2) consumption and increased Ki in both the control and the IsoPC groups at 1 hour after MCA occlusion. In the ischemic cortex (IC), the rCBF and O(2) consumption were significantly greater in the IsoPC group than in the control group (+40% and +41%, respectively), but they were similar in the contralateral cortex between the 2 groups. There was no difference in Ki between the groups in the IC or in the contralateral cortex. The increase of rCBF in the IC (+50%) was sustained in the IsoPC group at 3 hours after MCA occlusion. With iNOS inhibition, the increase of rCBF in the IC with isoflurane pretreatment became insignificant. Our data demonstrate that isoflurane pretreatment improved rCBF and increased the regional O(2) supply and consumption in the focal ischemic area but did not affect capillary permeability during the early stage of focal cerebral ischemia. The isoflurane-induced increase in rCBF in the ischemic area became insignificant with inhibition of iNOS.

Response to Letter by Bendszus et al

Response: We are grateful to Bendszus et al for their letter because their comments further improve the discussion of our article,1 raising important questions about the interpretation of MR signal loss at the early stage of focal cerebral ischemia. The authors indeed suggest that in this context the hypointense rim surrounding the ischemic lesion might be related to ongoing thrombus formation. This hypothesis seems likely to us because we did observe intravascular trapping of iron particles after Prussian blue staining at the early stages postischemia (<12 hours …

Effects of anti-VEGF antibody on blood–brain barrier disruption in focal cerebral ischemia

Since cerebral ischemia increases expression of vascular endothelial growth factor (VEGF) and exogenous VEGF can aggravate BBB disruption in cerebral ischemia, we hypothesized that inhibition of endogenous VEGF would attenuate BBB disruption. To test this hypothesis, rats were mechanically ventilated with isoflurane and a craniotomy (5 mm in diameter) was performed to expose the cerebral cortex. Anti-VEGF antibody was applied topically (75 μg) 1 h before middle cerebral artery (MCA) occlusion and additional anti-VEGF antibody was applied (25 μg) immediately after MCA occlusion (anti-VEGF group). For the control animals, normal saline was applied instead of anti-VEGF antibody on the surface of the cortex (control group). One hour after MCA occlusion, the transfer coefficient ( K i) of 14C-α-aminoisobutyric acid and volume of 3H-dextran (70,000 Da) distribution were determined to measure the degree of BBB disruption. There was no significant difference in vital signs, blood gases, and pericranial temperature between the control and the anti-VEGF group. In both of the groups, the K i of the ischemic cortex (IC) was higher than that of the corresponding contralateral cortex (CC) ( p < 0.05). The K i of the IC of the anti-VEGF group was significantly lower than that of the IC of the control group (− 34%, p < 0.05). The K i of the CC and pons were similar between these two groups. The data of volume of dextran distribution followed the same pattern as that of K i but without a statistical significance. Our data demonstrated that inhibition of endogenous VEGF by topical application of anti-VEGF antibody in the ischemic cortex decreased the K i of 14C-AIB and suggest that endogenous VEGF is in part responsible for the BBB disruption during the early stage of focal cerebral ischemia.

Effects of Anti-VEGF Antibody on Blood-Brain Barrier Disruption in Focal Cerebral Ischemia

Since cerebral ischemia increases expression of vascular endothelial growth factor (VEGF) and exogenous VEGF can aggravate BBB disruption in cerebral ischemia, we hypothesized that inhibition of endogenous VEGF would attenuate BBB disruption. To test this hypothesis, rats were mechanically ventilated with isoflurane and a craniotomy (5 mm in diameter) was performed to expose the cerebral cortex. Anti-VEGF antibody was applied topically (75 mug) 1 h before middle cerebral artery (MCA) occlusion and additional anti-VEGF antibody was applied (25 mug) immediately after MCA occlusion (anti-VEGF group). For the control animals, normal saline was applied instead of anti-VEGF antibody on the surface of the cortex (control group). One hour after MCA occlusion, the transfer coefficient (K(i)) of (14)C-alpha-aminoisobutyric acid and volume of (3)H-dextran (70,000 Da) distribution were determined to measure the degree of BBB disruption. There was no significant difference in vital signs, blood gases, and pericranial temperature between the control and the anti-VEGF group. In both of the groups, the K(i) of the ischemic cortex (IC) was higher than that of the corresponding contralateral cortex (CC) (p<0.05). The K(i) of the IC of the anti-VEGF group was significantly lower than that of the IC of the control group (-34%, p<0.05). The K(i) of the CC and pons were similar between these two groups. The data of volume of dextran distribution followed the same pattern as that of K(i) but without a statistical significance. Our data demonstrated that inhibition of endogenous VEGF by topical application of anti-VEGF antibody in the ischemic cortex decreased the K(i) of (14)C-AIB and suggest that endogenous VEGF is in part responsible for the BBB disruption during the early stage of focal cerebral ischemia.

Effects of VEGF and nitric oxide synthase inhibition on blood–brain barrier disruption in the ischemic and non-ischemic cerebral cortex

Objectives: This study was performed to compare the effects of exogenous vascular endothelial growth factor (VEGF) and nitric oxide synthase (NOS) inhibition on blood–brain barrier (BBB) disruption in the ischemic cortex (IC) and non-ischemic contralateral cortex (CC) during the early stage of focal cerebral ischemia in rats.Methods: A middle cerebral artery (MCA) was occluded after a craniotomy in each rat under isoflurane anesthesia. Two more craniotomies were performed over the contralateral non-ischemic hemisphere to expose cerebral cortex. For the control rats, the normal saline patches were applied to all three craniotomy holes (control group). To inhibit NOS, NG-nitro-L-arginine-methyl ester (L-NAME) (10 mg/kg) was administered i.v. 20 minutes after MCA occlusion (L-NAME group). In another group, VEGF (10−10 M) was topically applied 30 minutes after MCA occlusion on the IC as well as one of the holes of the contralateral cortex (VEGF group). To investigate the effects of the combination of VEGF and L-NAME, both L-NAME and VEGF were administered as described above (L-NAME+ VEGF group). The transfer coefficient (Ki) of 14C-α-aminoisobutyric acid and the volume of 3H-dextran (70000 Da) distribution were determined to measure the degree of BBB disruption at 1 hour after MCA occlusion.Results: In the control group, Ki of the IC was significantly higher than the contralateral cortex (CC) (p<0.005). VEGF application increased the Ki of the IC further when compared with the control group (+51%, p<0.05%). L-NAME administration produced no significant decrease in the Ki of the IC when compared with the control group. With L-NAME+ VEGF administration, the Ki of the IC became significantly lower than that of the VEGF alone (−38%, p<0.005). Thus, L-NAME produced a much greater decrease in the Ki of the IC in the VEGF treated than the control animals (p<0.05). In the non-IC, VEGF, L-NAME, or their combination did not affect BBB disruption. The volume of dextran distribution followed a similar pattern to Ki.Discussion: Our data suggest that even in the early stage of focal cerebral ischemia, the degree of BBB disruption in response to the exogenous VEGF is much greater in the ischemic than in the non-IC and that the mechanism of the increase of BBB disruption by VEGF in the IC involves the NOS pathway.

Predicting the pathological fate of focal cerebral ischemia using 1H-magnetic resonance spectroscopic imaging

To clarify regional difference in 1H magnetic resonance spectral changes in the acute stage of focal cerebral ischemia, and to assess whether any correlation exists between spectral changes in acute stage and pathological outcome in the chronic stage, we measured the non-volume selected 1H-MRSI serially in the acute stage of focal ischemia in rat brain and correlated histopathological findings. The focal ischemia was induced by intraluminal MCA thread occlusion. After induction of focal ischemia, 1H-MR Spectroscopic Images (MRSI) were taken serially up to 10 h after the occlusion. NAA in the peri-ischemic area was maintained. On the other hand, the decline of NAA in the ischemic lesion was linear and drastic during the first 10 h after MCA occlusion, and the rates of decline of NAA concentrations up to 10 h after induction of ischemia, calculated with linear regression, were 0.44 m mol/kg/h in the ischemic core and 0.29 m mol/kg/h in the ischemic rim ( p<0.05). Lactate accumulated significantly in all three areas. Decreasing depth of NAA during the acute stage of cerebral ischemia identifies the formation of the ischemic core and can be used as a predictor for histological outcome.

Pathology of cerebral ischaemia - mechanisms involved in neuronal damage

The following features of the ischaemic and postischaemic brain are the focus of interest: Development of acidosis, edema formation, calcium overload glutamate excitotoxicity, free radical formation and nitric oxide overproduction. The brain is critically dependent on its blood flow for a continuous supply of oxygen and glucose. Energy depletion has fundamental importance in the genesis of subsequent injurious events. Loss of ATP rapidly leads to a massive calcium influx and release of calcium from intracellular compartments. Extracellular concentrations of glutamate are markedly elevated in ischaemic brain tissue. Intracellular Ca2+ overload during ischemia has several deleterious consequences including the formation of reactive oxygen species. Nitrogen monoxide (NO) is an important mediator of cellular and molecular events which impacts the pathophysiology of cerebral ischemia. An increase in intracellular Ca2+ activates the enzyme NO synthase which catalyzes the synthesis of NO. NO is produced in neurons glia cells and vascular endothelium in central nervous system. Depending on its origin, its effects are varied. NO is a mediator having both neurotoxic and neuromodulator effects. Neuronal NO is the neurotoxic agent mediating glutamate toxicity and increasing acute ischaemic damage. Vascular NO as a potent vasodilator and an inhibitor of platelet aggregation, may be beneficial in the early stages of focal cerebral ischemia. There is increasing evidence that ischaemic brain injury secondary to arterial occlusion is characterized by acute local inflammation, which involves accumulation of polymorphonuclear neutrophils. Overexpression of inflammatory mediators such as cytokines, chemokines and adhesion molecules promotes recruitment of leukocytes in the ischaemic area.

Mismatch between lactate and the apparent diffusion coefficient of water in progressive focal ischemia.

In this study, we examined mismatch in the area indicated by the normal apparent diffusion coefficient (ADC) of water and increased lactate in the early stage of focal cerebral ischemia. Five rats were subjected to permanent middle cerebral artery (MCA) occlusion. Diffusion-weighted echo planar imaging (DWEPI) and proton echo planar spectroscopic imaging (EPSI) were performed from 20 to 170 min after MCA occlusion, and lactate and N-acetyl asparate images were obtained by EPSI. Postmortem histological analysis was also performed. The areas of increased lactate and normal ADC were observed in the surrounding border zone of ischemia at approximately 20 min after MCA occlusion. This initial lactate in the border zone was significantly higher than that in the normal area, but lower than that in the ischemic core, which showed a reduction of ADC. However, this area was progressively involved in the ischemic core at 170 min without any treatment. The lactate-ADC mismatch in the initial period of ischemia may offer unique diagnostic information for ischemic tissue at high risk, followed by progressive involvement in the ischemic core without treatment. Considering that the accumulation of initial lactate in this area was not excessive, our findings may suggest that the lactate-ADC mismatch in the early period of ischemia indicates potentially salvageable tissue at high risk, requiring aggressive treatment.

Time dependence of effect of nitric oxide synthase inhibition on cerebral ischemic damage.

Nitric oxide, a potent vasodilator and an inhibitor of platelet aggregation, may be beneficial in the early stages of focal cerebral ischemia as it may facilitate collateral blood flow to the ischemic territory. Accordingly, the effect of inhibition of nitric oxide synthesis on cerebral ischemic damage may vary depending on the timing of the inhibition relative to the induction of ischemia. We therefore studied the time course of the effect of nitric oxide synthesis inhibition on focal cerebral ischemic damage. The middle cerebral artery was permanently occluded in spontaneously hypertensive rats and the nitric oxide synthase (NOS) inhibitor nitro-L-arginine methyl ester (L-NAME) was administered systemically (3 mg/kg) < 5 min or 2, 3, or 6 h later. Arterial pressure, rectal temperature, plasma glucose, and hematocrit were monitored. Infarct volume was determined on thionin-stained sections 24 h after induction of ischemia. NOS activity was determined in cerebellum from the conversion of L-[3H]arginine to L-[3H]citrulline. Administration of L-NAME < 5 min after arterial occlusion increased the infarct volume by 23 +/- 14% (mean +/- SD; p < 0.05, analysis of variance), while administration of L-NAME at 2 or 6 h did not affect the size of the infarct (p > 0.05). L-NAME administration 3 h after induction of ischemia reduced neocortical infarct size by 14 +/- 11% (p < 0.05). L-NAME decreased cerebellar NOS activity comparably in all groups (range 16-25%). We conclude that the effects of inhibition of nitric oxide synthesis on focal cerebral ischemic damage are time dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood—Brain Barrier Permeability and Brain Concentration of Sodium, Potassium, and Chloride during Focal Ischemia

Brain edema formation during the early stages of focal cerebral ischemia is associated with an increase in both sodium content and blood-brain barrier (BBB) sodium transport. The goals of this study were to determine whether chloride is the principal anion that accumulates in ischemic brain, how the rate of BBB transport of chloride compares with its rate of accumulation, and whether the stimulation seen in BBB sodium transport is also seen with other cations. Focal ischemia was produced by occlusion of the middle cerebral artery (MCAO) in anesthetized rats. Over the first 6 h after MCAO, the amount of brain water in the center of the ischemic cortex increased progressively at a rate of 0.15 +/- 0.02 (SE) g/g dry wt/h. This was accompanied by a net increase in brain sodium (48 +/- 12 mumol/g dry wt/h) and a loss of potassium (34 +/- 7 mumol/g dry wt/h). The net rate of chloride accumulation (16 +/- 1 mumol/g dry wt/h) approximated the net rate of increase of cations. Three hours after MCAO, the BBB permeability to three ions (22Na, 36Cl, and 86Rb) and two passive permeability tracers ([3H]alpha-aminoisobutyric acid ([3H]AIB) and [14C]urea) was determined. Permeability to either passive tracer was not increased, indicating that the BBB was intact. The rate of 36Cl influx was 3 times greater and the rate of 22Na influx 1.8 times greater than their respective net rates of accumulation in ischemic brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamics of extracellular metabolites in the striatum after middle cerebral artery occlusion in the rat monitored by intracerebral microdialysis.

The aim of this study was to measure changes in the extracellular fluid (ECF) concentration of lactate, pyruvate, purines, amino acids, dopamine, and dopamine metabolites in the striatum of rats subjected to focal cerebral ischemia, using intracerebral microdialysis as the sampling technique. Microdialysis probes were inserted into the lateral part of the caudate-putamen bilaterally 2 h before the experiment. Ischemia was induced by permanent middle cerebral artery occlusion (MCAO) on the left side. Microdialysis samples were analyzed by high performance liquid chromatography. Following MCAO, the concentration of lactate, adenosine, inosine, and hypoxanthine rose markedly in the ECF on the occluded side, while there was no significant change in pyruvate. These changes were accompanied by dramatically elevated levels of aspartate, glutamate, taurine, gamma-aminobutyric acid, and dopamine. There was also a marked increase in alanine/tyrosine, while minor or no changes occurred with other amino acids. Concomitantly, the ECF level of the dopamine metabolites 3,4-dihydroxyphenylacetate and homovanillic acid decreased. There was no significant increase in any of the metabolites measured on the right, nonoccluded side. In relation to the concept of excitotoxicity in brain ischemia, it is concluded that during the acute stage of focal cerebral ischemia, the ECF is flooded with both potentially harmful (e.g., aspartate, glutamate, and DA) and protective (e.g., taurine, GABA, and adenosine) agents. The relative importance of these events for the development of cell death in the ischemic penumbra needs to be elucidated. In addition, lactate, inosine, and hypoxanthine, measured in the ECF by intracerebral microdialysis, may prove to have diagnostic and/or prognostic value in neurometabolic monitoring of the ischemic brain.