nitroarginine and Brain-Ischemia

Remote ischemic postconditioning (RIPoC) attenuates ischemia/reperfusion (I/R) injury in the heart, lung and hind limb. RIPoC performed in the hind limb reduces brain injury following focal cerebral ischemia in rats. Whether RIPoC has a neuroprotective effect with respect to global cerebral I/R injury is, however, unknown, and the mechanism of neuroprotection needs further elucidation. Here we investigated whether RIPoC could reduce global cerebral I/R injury in rats and whether this neuroprotective effect was induced by up-regulating endothelial nitric oxide synthase (eNOS) through the phosphatidylinositol-3 kinase/Akt (PI3K/Akt) pathway. Global cerebral ischemia was performed via 8min of four-vessel occlusion. Neuronal density, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells and expression of Bcl-2 and Bax in the hippocampal CA1 region were assessed after reperfusion. Morris water maze task was used to quantify spatial learning and memory deficits after reperfusion. The expression of eNOS, phosphorylated eNOS (Ser1177), Akt and phosphorylated Akt (Ser473) in the CA1 region was measured after reperfusion. RIPoC significantly attenuated delayed neuronal death and reduced the spatial learning and memory deficits associated with global cerebral ischemia. Pre-administration of N(ω)-nitro-l-arginine methyl ester (a nonselective NOS inhibitor) significantly abolished the neuroprotective effect of RIPoC. Moreover, pre-administration of LY294002 (a highly selective inhibitor of PI3K) not only significantly reversed the neuroprotective effect of RIPoC, but also obviously inhibited the up-regulation of eNOS induced by RIPoC. Our findings suggest that RIPoC protects the brain against global cerebral I/R injury and that this neuroprotection is mediated by up-regulating eNOS through the PI3K/Akt pathway.

Topics: Analysis of Variance; Animals; Avoidance Learning; Brain; Brain Infarction; Brain Ischemia; Cell Death; Chromones; Disease Models, Animal; Enzyme Inhibitors; Gene Expression Regulation; In Situ Nick-End Labeling; Ischemic Postconditioning; Male; Maze Learning; Morpholines; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type III; Nitroarginine; Oncogene Protein v-akt; Phosphatidylinositol 3-Kinase; Rats; Rats, Sprague-Dawley; Reaction Time; Reperfusion Injury

The role of SK(Ca) and IK(Ca) channels in myogenic tone and endothelium-derived hyperpolarizing factor (EDHF) responsiveness was investigated under control conditions and after ischemia and reperfusion in parenchymal arterioles (PA) versus middle cerebral arteries (MCA).. MCA and PA were dissected from male Wistar rats that were ischemic for 1 hour with 24 hours of reperfusion (n=12) or sham controls (n=12). Basal tone and reactivity to apamin (300 nmol/L), TRAM-34 (1.0 micromol/L), and nitro-L-arginine (0.1 mmol/L) were compared in PA and MCA pressurized to 40 mm Hg and 75 mm Hg, respectively. SK(Ca) and IK(Ca) channel mRNA expression was measured using real-time PCR.. PA developed greater basal tone than MCA (42+/-4% versus 19+/-3%; P<0.01). Addition of apamin and TRAM-34 increased tone of PA by 25+/-3% and 16+/-2%, respectively, whereas MCA had no response to either inhibitor. After ischemia and reperfusion, the response to nitric oxide synthase inhibition (NOS) was diminished in PA, whereas EDHF responsiveness was preserved. In addition, stimulated EDHF dilation was partially reversed by apamin and completely reversed by TRAM-34 in both control and ischemic PA. SK(Ca) and IK(Ca) channel mRNA expression was similar in PA and MCA and not altered by ischemia and reperfusion. However, IK(Ca) channel mRNA expression was 4- to 5-fold greater than SK(Ca) channels.. It appears that SK(Ca) and IK(Ca) channel activity diminishes basal tone of PA, but not MCA. The preservation of EDHF responsiveness of PA after ischemia and reperfusion suggests an important role for this vasodilator under conditions when NOS is inhibited.

Topics: Animals; Apamin; Arterioles; Biological Factors; Brain Ischemia; Calcimycin; Disease Models, Animal; Enzyme Inhibitors; Intermediate-Conductance Calcium-Activated Potassium Channels; Ionophores; Male; Middle Cerebral Artery; Nitric Oxide; Nitroarginine; Pyrazoles; Rats; Rats, Wistar; Reperfusion Injury; RNA, Messenger; Small-Conductance Calcium-Activated Potassium Channels; Vasodilation

We investigated the effect of ischemia and reperfusion on the vasoactive function of penetrating brain parenchymal arterioles under pressurized conditions.. Parenchymal arterioles (< 50 microm in diameter) from within the middle cerebral artery territory were dissected from male Wistar rats that were either nonischemic control (n = 16) or ischemic for one hour and reperfused for 24 hours (n = 16) by temporary filament occlusion of the middle cerebral artery. Arterioles were mounted on glass cannulas within an arteriograph chamber that allowed for the measurement of lumen diameter and control over intravascular pressure.. After one hour of equilibration at 10 mmHg, spontaneous myogenic tone developed in both groups of animals, constricting control arterioles from 69 +/- 9 to 49 +/- 11 microm (29.5 +/- 10.2%) and ischemic arterioles from 66 +/- 9 to 45 +/- 11 microm (33.1 +/- 14.1%); p > 0.05. Contraction to the nitric oxide synthase inhibitor nitro-L-arginine (10(-4)M) was significantly diminished in ischemic arterioles, constricting only 3.2 +/- 3.3 vs. 15.6 +/- 12.5% in control arterioles (p = 0.017). Both groups dilated to nifedipine; however, the response was significantly diminished after ischemia. The EC50 for nifedipine in control arterioles was 3.54 +/- 0.11 vs. 9.90 +/- 0.71 nM for ischemic arterioles (p = 0.024).. These findings demonstrate that functional changes occur in brain parenchymal arterioles after ischemia and reperfusion, a result that may significantly influence stroke outcome by altering blood flow to an ischemic region.

Topics: Animals; Arterioles; Brain; Brain Ischemia; Cerebrovascular Circulation; Enzyme Inhibitors; Male; Middle Cerebral Artery; Nifedipine; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Wistar; Reperfusion Injury; Stroke; Vasoconstriction; Vasodilator Agents

To evaluate the effect of NG-nitro-L-arginine (L-NA) on inflammatory factor and neuronal apoptosis after focal cerebral ischemic injury in rats and the possible mechanism of protective effect of L-NA against cerebral ischemic injury.. Thirty male SD rats weighing 250-280 g were randomly divided into three groups (n=10): (1) Sham operated group (SH), (2) Ischemic group (IS), (3) L-NA group. In L-NA group L-NA 20 mg/kg was given intraperitoneally twice a day for 3 consecutive days. In IS group normal saline was given instead of L-NA. Focal cerebral ischemia was produced by middle cerebral artery occlusion (MCAO) for 12 h. A nylon thread with rounded tip which was inserted into left internal carotid artery cranially until resistance was felt. The distance from bifurcation of common carotid artery to the tip of the thread was about 18-19 mm. Focal cerebral ischemia was confirmed by left Horner's syndrome and right side hemiplegia. In SH group the carotid artery was exposed but no thread was inserted. The expression of TNF-alpha was determined by immunochemistry and the content of IL-1beta was measured by radio immunity. The Bcl-2 and Bax protein expression were detected by flow cytometry.. The expression of TNF-alpha and the content of IL-1 beta were markedly increased after MCAO. Significantly increased DNA fragmentation indication of apoptosis was detected after MCAO. The expression of TNF-alpha and the content of IL-1 beta was significantly lower in L-NA group than in IS group. The percentage of apoptosis cells and expression of Bax protein were markedly lower in L-NA group than in IS group but still significantly higher than in SH group. The expression of Bcl-2 protein was markedly higher in L-NA group than in IS group. There was no significant difference in the expression of Bcl-2 protein between IS and SH group.. L-NA could inhibit the increase in the expression of TNF-alpha and the content of IL-1beta, and protect neurons from apoptosis induced by focal cerebral ischemia through increasing the Bcl-2 protein expression and inhibiting the Bax protein expression.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Brain Injuries; Brain Ischemia; Interleukin-1beta; Male; Nitroarginine; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Sprague-Dawley; Tumor Necrosis Factor-alpha

In the present study, we investigated the effects of N(G)-nitro-L-arginine (L-NAME), an inhibitor of nitric oxide synthase, on repeated cerebral ischemia-induced impairment of spatial memory of the 8-arm radial maze in rats. Repeated ischemia (10 min ischemia x 2 times with 1 h interval) impaired the spatial memory in the 8-arm radial maze test and produced apoptosis in the hippocampus 7 days after final occlusion, and gradually increased the NO(x)(-) levels approximately 30-180 min after the second reperfusion. Post-ischemic administration of L-NAME at a dose of 50 mg/kg, i.p. 30 min following the second occlusion, significantly attenuated the repeated ischemia-induced impairment of spatial memory in the 8-arm radial maze test and suppressed apoptosis in the hippocampus, and also significantly suppressed a delayed increase in the NO(x)(-) levels induced by repeated ischemia. However, pre-ischemic administration of L-NAME at a dose of 50 mg/kg, i.p. 30 min before the first occlusion, caused about 90% mortality (the mortality rate of vehicle-treated group was 10%). These results suggest that the delayed generation of NO(x)(-) may cause spatial memory impairment and induction of apoptosis in the hippocampus in rats subjected to repeated ischemia.

Topics: Animals; Apoptosis; Brain Ischemia; Disease Models, Animal; Enzyme Inhibitors; Hippocampus; Injections, Intraperitoneal; Injections, Intraventricular; Maze Learning; Memory; Microdialysis; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Wistar; Time Factors

The principal aim of this study was to examine the relative contributions from the neuronal and endothelial isoforms of nitric oxide synthase (nNOS and eNOS, respectively) in their capacity to modulate intra-ischemic cerebral blood flow (CBF) changes, in the ischemically vulnerable hippocampus and striatum. CBF changes were monitored, using laser-Doppler flowmetry, in rats subjected to 30 min of forebrain ischemia (right common carotid occlusion+hemorrhagic hypotension). Rats were pretreated with a selective nNOS inhibitor (ARR 17477), a NOS inhibitor that blocks both eNOS and nNOS (N(G)-nitro-L-arginine; L-NNA), or saline (control). In initial experiments, where ischemic MABP was targeted to exactly 30 mmHg, NOS inhibition reduced intra-ischemic cortical CBF from the control level of approximately 20% of baseline to 3% (L-NNA) or 6% (ARR 17477) of baseline. The statistically similar effects of the two NOS inhibitors confirmed that nNOS is the predominant NO source supporting intra-ischemic vasodilation in the cortex. In subsequent experiments, CBF was measured in the right hippocampus, and striatum, as well as the cortex, and, to reduce data variability, blood withdrawal was adjusted to achieve an intra-ischemic cortical CBF of 20% (controls) or 5% (NOS inhibited rats) of baseline. In those groups, mean ischemic MABP levels ranged from 28 to 32 mmHg. In controls, intra-ischemic CBF fell to 20%, 45%, and 47% of baseline in the cortex, hippocampus, and striatum, respectively. With nNOS inhibition, intra-ischemic CBF was further reduced to 5%, 15%, and 18% of baseline, respectively. However, with combined eNOS/nNOS inhibition, the CBF values were 5%, 37%, and 21%, respectively. These results suggest that the nNOS contribution to intra-ischemic vasodilation in vulnerable regions is substantially greater than eNOS. The significantly higher intra-ischemic CBF level in the hippocampus in combined eNOS/nNOS vs nNOS-inhibited rats may relate, in contrast to other regions, to a low eNOS influence on vascular function in that structure and CBF redistribution to the hippocampus when eNOS activity is blocked globally.

Topics: Amidines; Animals; Blood Pressure; Brain Ischemia; Cerebrovascular Circulation; Corpus Striatum; Enzyme Inhibitors; Female; Hippocampus; Laser-Doppler Flowmetry; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type III; Nitroarginine; Prosencephalon; Rats; Rats, Sprague-Dawley

The cerebral endothelial cells (ECs) are a primary target of hypoxic or ischemic brain insults. EC damage may contribute to postischemic secondary injury. Massive production of NO after inducible NO synthase (iNOS) expression has been implicated in cell death. This study aimed to characterize bovine cerebral EC death in relation to iNOS expression after oxygen-glucose deprivation (OGD) in vitro.. OGD in bovine cerebral ECs in culture was induced by deleting glucose in the medium and by incubating the cells in a temperature-controlled anaerobic chamber. The extent of cell death was assessed by trypan blue exclusion, MTT assay, and LDH release. ELISA, gel electrophoresis, and staining by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling were used to examine DNA fragmentation. The expression of iNOS mRNA and protein was detected by reverse transcription-polymerase chain reaction and Western blotting, respectively. Nitrotyrosine expression was confirmed with Western blot analysis and immunostaining.. Bovine cerebral EC death was dependent on the duration of OGD and showed selected biochemical, morphological, and pharmacological features suggestive of apoptosis. OGD also induced the expression of iNOS mRNA and protein in bovine cerebral ECs. Increased expression of nitrotyrosine, the product formed by peroxynitrite reaction with proteins, was also detected after OGD. The involvement of iNOS in EC death was suggested by partial reduction of cell death by NO synthase inhibitors, including L-N(G)-(1-iminoethyl)ornithine and nitro-L-arginine, and an NO scavenger, the Fe(2+)-N-methyl-D-glucamine dithiocarbamate complex.. OGD-induced bovine cerebral EC death involves an apoptotic process. Induction of iNOS with subsequent peroxynitrite formation may contribute to bovine cerebral EC death caused by OGD.

Topics: Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Blood-Brain Barrier; Brain; Brain Ischemia; Caspase Inhibitors; Cattle; Cells, Cultured; Chelating Agents; Cysteine Proteinase Inhibitors; Cytochrome c Group; DNA Fragmentation; Endothelium, Vascular; Free Radicals; Gene Expression Regulation, Enzymologic; Glucose; In Situ Nick-End Labeling; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitroarginine; Oxygen; RNA, Messenger; Sorbitol; Spin Labels; Thiocarbamates; Tyrosine

Neuroprotection against cerebral ischemia can be realized if the brain is preconditioned by previous exposure to a brief period of sublethal ischemia. The present study was undertaken to test the hypothesis that nitric oxide (NO) produced from the neuronal isoform of NO synthase (NOS) serves as a necessary signal for establishing an ischemia-tolerant state in brain. A newborn rat model of hypoxic preconditioning was used, wherein exposure to sublethal hypoxia (8% oxygen) for 3 hours renders postnatal day (PND) 6 animals completely resistant to a cerebral hypoxic-ischemic insult imposed 24 hours later. Postnatal day 6 animals were treated 0.5 hour before preconditioning hypoxia with the nonselective NOS inhibitor L-nitroarginine (2 mg/kg intraperitoneally). This treatment, which resulted in a 67 to 81% inhibition of calcium-dependent constitutive NOS activity 0.5 to 3.5 hours after its administration, completely blocked preconditioning-induced protection. However, administration of the neuronal NOS inhibitor 7-nitroindazole (40 mg/kg intraperitoneally) before preconditioning hypoxia, which decreased constitutive brain NOS activity by 58 to 81%, was without effect on preconditioning-induced cerebroprotection, as was pretreatment with the inducible NOS inhibitor aminoguanidine (400 mg/kg intraperitoneally). The protective effects of preconditioning were also not blocked by treating animals with competitive [3-(2-carboxypiperazin-4-yl)propyl-1-phosphonate; 5 mg/kg intraperitoneally] or noncompetitive (MK-801; 1 mg/kg intraperitoneally) N-methyl-D-aspartate receptor antagonists prior to preconditioning hypoxia. These findings indicate that NO production and activity are critical to the induction of ischemic tolerance in this model. However, the results argue against the involvement of the neuronal NOS isoform, activated secondary to a hypoxia-induced stimulation of N-methyl-D-aspartate receptors, and against the involvement of the inducible NOS isoform, but rather suggest that NO produced by the endothelial NOS isoform is required to mediate this profound protective effect.

Topics: Animals; Animals, Newborn; Brain Ischemia; Calcium; Dizocilpine Maleate; Enzyme Inhibitors; Guanidines; Hypoxia; Indazoles; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Oxygen; Piperazines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate

The present study was designed to examine the effects of inhibition of nitric oxide synthase on cerebral energy metabolism after hypoxia-ischemia in newborn piglets. Ten 1- to 3-d-old piglets received N(omega)-nitro-L-arginine (NNLA), an inhibitor of nitric oxide synthase (NNLA-hypoxia, n = 5), or normal saline (hypoxia, n = 5) 1 h before cerebral hypoxia-ischemia. After the infusion, hypoxia-ischemia was induced by bilateral occlusion of the carotid arteries and decreasing FiO2 to 0.07 and maintained for 60 min. Thereafter, animals were resuscitated and ventilated for another 3 h. Using 1H- and 31P-magnetic resonance spectroscopy, cerebral energy metabolism was measured in vivo at 15-min intervals throughout the experiment. Phosphocreatine to inorganic phosphate ratios decreased from 2.74 +/- 0.14 to 0.74 +/- 0.36 (hypoxia group) and 2.32 +/- 0.17 to 0.18 +/- 0.10 (NNLA-hypoxia group) during hypoxia-ischemia. Thereafter, phosphocreatine to inorganic phosphate ratios returned rapidly to baseline values in the hypoxia group, but remained below baseline values in the NNLA-hypoxia group. Intracellular pH decreased during hypoxia-ischemia and returned to baseline values on reperfusion in both groups. Intracellular pH values were lower in the NNLA-hypoxia group (p < 0.001, ANOVA). Lactate was not present during the baseline period. After hypoxia-ischemia, lactate to N-acetylaspartate ratios increased to 1.34 +/- 0.28 (hypoxia group) and 2.22 +/- 0.46 (NNLA-hypoxia group). Lactate had disappeared after 3 h of reperfusion in the hypoxia group, whereas lactate to N-acetylaspartate ratios were 1.37 +/- 1.37 in the NNLA-hypoxia group. ANOVA demonstrated a significant effect of NNLA on lactate to N-acetylaspartate ratios (p < 0.001). Inhibition of nitric oxide synthase by NNLA tended to compromise cerebral energy status during and after cerebral hypoxia-ischemia in newborn piglets.

Topics: Animals; Animals, Newborn; Brain; Brain Ischemia; Cerebrovascular Circulation; Disease Models, Animal; Energy Metabolism; Enzyme Inhibitors; Hydrogen-Ion Concentration; Hypoxia, Brain; Lactic Acid; Magnetic Resonance Spectroscopy; Nitric Oxide Synthase; Nitroarginine; Phosphates; Phosphocreatine; Swine

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(G)Nitroarginine (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.

Topics: Animals; Brain; Brain Ischemia; Cell Survival; Enzyme Inhibitors; Indazoles; Male; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitroarginine; Rats; Rats, Wistar; Reperfusion; Time Factors

The aim of this study was to investigate the role of nitric oxide in metabolic disturbances induced in brain tissue of fetal guinea pigs by oxygen-glucose deprivation. Experiments were performed on hippocampal slices so as to exclude the effects of nitric oxide on the cardiovascular system. Metabolic disturbances were assessed by measuring changes in energy metabolism and protein synthesis after different periods of oxygen-glucose deprivation (OGD). Ten min after OGD of 40 min duration, the concentration of cGMP in tissue slices rose from 1.35 +/- 0.38 to 18.6 +/- 1.04 pmol/mg protein (P < 0.05). This rise was almost completely inhibited by the addition of 100 microM N-nitro-L-arginine (NNLA), indicating that NO-synthase was strongly activated after OGD in fetal brain tissue. However, addition of NNLA improved neither protein synthesis nor energy metabolism measured 12 h after OGD. Thus, nitric oxide does not appear to contribute directly to processes leading to metabolic disturbances induced by transient ischemia in immature brain tissue.

Topics: Adenosine Triphosphate; Animals; Brain Ischemia; Cell Hypoxia; Cyclic GMP; Energy Metabolism; Fetus; Glucose; Guinea Pigs; Hippocampus; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Organ Culture Techniques; Oxygen

Recent studies indicate that leukocytes are important contributors to secondary vascular and parenchymal injury after cerebral ischemia. The present study was undertaken to define nitric oxide (NO)-based mechanisms that regulate leukocyte-endothelial interactions in the cerebral vasculature, how these mechanisms are affected by cerebral ischemia, and whether NO-based therapies can affect postischemic leukocyte dynamics.. Leukocyte adherence to pial venules of anesthetized newborn piglets was quantified by in situ fluorescence videomicroscopy through closed cranial windows during basal conditions and during reperfusion after 9 minutes of asphyxia. Nitric oxide synthase (NOS) was inhibited by local window superfusion of L-nitroarginine; superfusion of sodium nitroprusside was used to donate NO.. Local inhibition of NOS under resting conditions increased leukocyte-endothelial adherence 2.2-fold and 3.9-fold over baseline values after 1 hour and 2 hours, respectively; this response was completely blocked by cosuperfusion with L-arginine. Cosuperfusion of superoxide dismutase reversed L-nitroarginine-induced leukocyte adherence by 89% and 63% at these respective time points. The extent of acute leukocyte adherence elicited by NOS inhibition was similar in magnitude to that observed during the initial 2 hours of reperfusion after asphyxia. Leukocyte adherence was not additionally increased in asphyxic animals treated with L-nitroarginine. Sodium nitroprusside robustly inhibited asphyxia-induced leukocyte adherence back to control levels.. NO exerts a tonic antiadherent effect in the cerebral microcirculation by inactivation of adherence-promoting superoxide radical formation. Cerebral ischemia is associated with an inhibition of NOS or lower levels of NO, which results in leukocyte-endothelial adherence that can be prevented by NO donors. The latter may be useful therapeutically to prevent the purported vascular and parenchymal dysfunction and injury caused by activated leukocytes in ischemic brain.

Topics: Animals; Animals, Newborn; Brain Ischemia; Cell Adhesion; Endothelium, Vascular; Enzyme Inhibitors; Leukocytes; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitroprusside; Pia Mater; Reference Values; Swine; Vasodilator Agents; Venules

We investigated the combined effect of increased brain topical K+ concentration and reduction of the nitric oxide (NO.) level caused by nitric oxide scavenging or nitric oxide synthase (NOS) inhibition on regional cerebral blood flow and subarachnoid direct current (DC) potential. Using thiopental-anesthetized male Wistar rats with a closed cranial window preparation, brain topical superfusion of a combination of the NO. scavenger hemoglobin (Hb; 2 mmol/L) and increased K+ concentration in the artificial cerebrospinal fluid ([K+]ACSF) at 35 mmol/L led to sudden spontaneous transient ischemic events with a decrease of CBF to 14+/-7% (n=4) compared with the baseline (100%). The ischemic events lasted for 53+/-17 minutes and were associated with a negative subarachnoid DC shift of -7.3+/-0.6 mV of 49+/-12 minutes' duration. The combination of the NOS inhibitor N-nitro-L-arginine (L-NA, 1 mmol/L) with [K+]ACSF at 35 mmol/L caused similar spontaneous transient ischemic events in 13 rats. When cortical spreading depression was induced by KCl at a 5-mm distance, a typical cortical spreading hyperemia (CSH) and negative DC shift were measured at the closed cranial window during brain topical superfusion with either physiologic artificial CSF (n=5), or artificial CSF containing increased [K+]ACSF at 20 mmol/L (n=4), [K+]ACSF at 3 mmol/L combined with L-NA (n=10), [K+]ACSF at 10 mmol/L combined with L-NA (five of six animals) or [K+]ACSF at 3 mmol/L combined with Hb (three of four animals). Cortical spreading depression induced longlasting transient ischemia instead of CSH, when brain was superfused with either [K+]ACSF at 20 mmol/L combined with Hb (CBF decrease to 20+/-20% duration 25+/-21 minutes, n=4), or [K+]ACSF at 20 mmol/L combined with L-NA (n=19). Transient ischemia induced by NOS inhibition and [K],ACSF at 20 mmol/L propagated at a speed of 3.4+/-0.6 mm/min, indicating cortical spreading ischemia (CSI). Although CSH did not change oxygen free radical production, as measured on-line by in vivo lucigenin-enhanced chemiluminescence, CSI resulted in the typical radical production pattern of ischemia and reperfusion suggestive of brain damage (n=4). Nimodipine (2 microg/kg body weight/min intravenously) transformed CSI back to CSH (n=4). Vehicle had no effect on CSI (n=4). Our data suggest that the combination of decreased NO. levels and increased subarachnoid K+ levels induces spreading depression with acute ischemic CBF response. Thus, a disturbed coupling

Topics: Animals; Brain Ischemia; Cerebrovascular Circulation; Enzyme Inhibitors; Free Radical Scavengers; Hemoglobins; Male; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Potassium; Rats; Rats, Wistar; Subarachnoid Space

Topics: Animals; Animals, Newborn; Brain Ischemia; Cerebral Cortex; Enzyme Inhibitors; Glucose; In Vitro Techniques; Mitochondria; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Oxygen; Rats

Post-hypoxic-ischemic (HI) reperfusion induces endothelium and neurons to produce excessive amounts of nitric oxide and superoxide, leading to peroxynitrite formation, release of protein-bound metal ions (i.e. iron), and cytotoxic oxidants. We produced severe HI in 18 newborn lambs and serially determined plasma prooxidants (non-protein-bound iron), lipid peroxidation (malondialdehyde), and antioxidative capacity [ratio of ascorbic acid/dehydroascorbic acid (AA/DHA), alpha-tocopherol, sulfhydryl groups, allantoin/uric acid ratio, and vitamin A] in blood effluent from the brain before and at 15, 60, 120, and 180 min after HI. The lambs were divided in three groups: six received a placebo (CONT), six received low dose (10 mg/kg/i.v.) N omega-nitro-L-arginine (NLA-10) to block nitric oxide production, and six received high dose NLA (40 mg/kg/i.v.; NLA-40), immediately after completion of HI. Non-protein-bound iron increased in all groups after HI but was significantly lower in both NLA groups at 180 min post-HI (p < 0.05), the AA/DHA ratio showed a consistent decrease in CONT (at 60 min post-HI, p < 0.05), but remained stable in NLA lambs. alpha-Tocopherol decreased steadily in the CONT, but not in the NLA lambs [180 post-H: 1.9 +/- 0.9 versus 4.2 +/- 0.7 microM (NLA-40), p < 0.05). Malondialdehyde was significantly higher in CONT lambs 120 min post-H compared with NLA groups [0.61 +/- 017 versus 0.44 +/- 0.05 microM (NLA-40), p < 0.05]. Vitamin A and sulfhydryl groups did not differ among groups. We conclude that post-H inhibition of nitric oxide synthesis diminishes non-protein-bound iron increment and preserves antioxidant capacity.

Topics: Animals; Animals, Newborn; Antioxidants; Brain Ischemia; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Enzyme Inhibitors; Hypoxia, Brain; Lipid Peroxidation; Nitric Oxide Synthase; Nitroarginine; Oxidation-Reduction; Oxidative Stress; Reperfusion Injury; Sheep

The present study aimed to examine the effects of N omega-nitro-L-arginine (LNA) on the early ischemic neuronal damage (EIND). All the experiments were carried out under general anesthesia, maintaining the blood gases and the body temperature within the physiological ranges. The local CBF, the topographically corresponding cortical specific gravity, and the volume of EIND were determined in each rat, which was subjected to prolonged or temporary occlusion of middle cerebral artery (MCA) using our original miniclip. Significant cortical edema developed only in the brain area where the local CBF value was below 200 ml 100 g-1 min-1. The prolonged MCA occlusion for 1, 2, and 4 h induced a time-dependent increase in the severity of cortical edema and the volume of EIND. Removal of the clip invariably induced recirculation. Compared to that induced by 4 h prolonged ischemia, the brain damage was improved by 1 h MCA occlusion followed by 3 h recirculation, whereas it was significantly worsened by 2 h ischemia followed by 2 h recirculation. While LNA [1 mg, i.p., given two times during the experiment] only partially inhibited the activity of brain nitric oxide synthase, it remarkably ameliorated EIND of both prolonged ischemia and recirculation in this model. The above findings indicate the pathogenic role of nitric oxide in prolonged ischemia as well as recirculation.

Topics: Animals; Blood Pressure; Brain Ischemia; Cerebral Cortex; Chronic Disease; Enzyme Inhibitors; Neurons; Nitric Oxide Synthase; Nitroarginine; Rats; Reperfusion Injury; Specific Gravity; Time Factors

To assess the role of nitric oxide (NO) in cerebral ischemia, we investigated the effect of L-arginine, a substrate of NO synthase (NOS), and NG-nitro-L-arginine (L-NNA), a NOS inhibitor, on neuronal death in the CA1 hippocampal region. Seventy-two Mongolian gerbils were used in the study. Both carotid arteries were occluded for 4 min to induce forebrain ischemia. Temporal muscle temperature was strictly maintained at 37.5 +/- 0.3 degrees C during the ischemia. L-arginine (10 and 100 mg kg-1) or L-NNA (1, 10 and 100 mg kg-1) was administered intraperitoneally 4 times: 30 min before, 3 h, 6 h and 24 h after induction of ischemia. Four days after ischemic insult, the animals were perfusion-fixed, and the neuronal densities in the medial, middle and lateral CA1 subfield were estimated. Average neuronal cell density of the control group was 2-3 mm in each subfield. L-arginine at doses of 10 and 100 mg kg-1 did not prevent neuronal death. L-NNA at doses of 1 and 10 mg kg-1 did not protect neuronal cells from ischemia either. However, in ischemia gerbils treated with 100 mg kg-1 L-NNA, the average neuronal cell density in the lateral CA1 subfield was 54.4 +/- 19.1, L-NNA (100 mg kg-1) significantly (p < 0.05) reduced the occurrence of neuronal death in the lateral CA1 subfield. The present results suggest that NO plays an important role in the development of neuronal injury after global ischemia.

Topics: Animals; Arginine; Body Temperature; Brain Ischemia; Cell Death; Enzyme Inhibitors; Gerbillinae; Hippocampus; Male; Neurons; Nitric Oxide Synthase; Nitroarginine; Sodium Bicarbonate

Since an excessive production of nitric oxide upon reperfusion/reoxygenation may play an important role in post-hypoxic-ischemic (HI) brain injury, we investigated whether immediate post-HI blockade of nitric oxide synthesis by N-omega-nitro-L-arginine (NLA) may reduce this injury. In 18 newborn lambs, subjected to severe HI, changes from pre-HI values were measured for carotid blood flow (Qcar [ml/min]) as a measure of changes in brain blood flow, (relative) cerebral metabolic rate of oxygen (CMRO2), and electrocortical brain activity (ECBA) at 15, 60, 120 and 180 min after HI. Upon completion of HI, at the onset of reperfusion and reoxygenation, 6 lambs received a placebo (control group), 6 low-dose NLA (10 mg/kg i.v., NLA-10 group), and 6 high-dose NLA (40 mg/kg i.v., NLA-40 group). Histological damage to cerebellar Purkinje cells was assessed after termination of the experiment. Only the control group showed a distinct initial post-HI cerebral hyperperfusion. From 60 min after HI onward Qcar was decreased to about 75% of pre-HI Qcar in all 3 groups, although none of these changes in Qcar reached statistical significance. Despite the decreased Qcar in all 3 groups, only the control group showed a significantly decreased CMRO2. ECBA and its bandwidth decreased in all groups, but only recovered in the NLA-10 group 180 min after HI. The brain to body mass ratio (%) and percentage necrotic Purkinje cells were, respectively: 15.3 +/- 0.8 and 56 +/- 10 (control group); 12.5 +/- 1.2 and 36 +/- 9 (NLA-10 group), and 11.3 +/- 1.0 (p < 0.05 vs. the control group) and 35 +/- 14 (NLA-40 group). Since post-HI reperfusion injury of the brain has been characterized by a decreased CMRO2 and electrical brain activity, we conclude that preservation of CMRO2 in both NLA groups, but a recovery of ECBA and its bandwidth only in the NLA-10 group, suggests that NLA, and especially low-dose NLA, may reduce post-HI brain injury.

Topics: Animals; Animals, Newborn; Brain; Brain Ischemia; Dose-Response Relationship, Drug; Electroencephalography; Enzyme Inhibitors; Hypoxia, Brain; Nitric Oxide Synthase; Nitroarginine; Reference Values; Regional Blood Flow; Reperfusion Injury; Sheep; Time Factors

Inhibition of nitric oxide (NO) production may reduce post-hypoxic-ischemic (HI) neonatal brain damage, but may also induce pulmonary hypertension by inhibiting endogenous NO production in the pulmonary vascular bed. The aim of this study was to evaluate the effect of nitric oxide inhibition on pulmonary artery pressure and oxygen need after hypoxic ischemia. Severe HI was produced in 18 newborn lambs. After completion of HI the lambs were divided into three groups of 6 animals receiving either placebo (Cont), low dose N omega-nitro-L-arginine (10 mg/kg i.v., NLA-10) or high dose (40 mg/kg i.v., NLA-40) to block NO production. Pulmonary artery pressure (Pap), aortic pressure, blood gases, inspiratory oxygen concentration and ventilator settings were recorded before and 15, 60, 120 and 180 min after HI. Mean Pap rose initially significantly as compared to baseline in all groups at 15 min post-HI, decreased to normal in Cont but not in treated animals; 180 min post-HI mean Pap was significantly higher in both treated groups as compared to control (NLA-10: 32 mm Hg, NLA-40: 34 mm Hg, Cont: 25 mm Hg, p < 0.05 for NLA-10 and NLA-40 vs. Cont). Moreover, in both NLA-treated groups the oxygenation index was significantly elevated 120 and 180 min post-HI as compared to those of the Cont group. NO synthase inhibition after HI causes a prolonged increase in pulmonary artery pressure leading to a higher oxygen need.

Topics: Animals; Blood Gas Analysis; Brain; Brain Ischemia; Cohort Studies; Dose-Response Relationship, Drug; Enzyme Inhibitors; Hydrogen-Ion Concentration; Hypoxia, Brain; Nitric Oxide Synthase; Nitroarginine; Oxygen Consumption; Pulmonary Artery; Pulmonary Wedge Pressure; Sheep; Time Factors

The involvement of nitric oxide (NO) in the development of ischemic cytotoxic edema was investigated by inhibiting nitric oxide synthase (NOS) activity with N omega-nitro-L-arginine (NLA). Bilateral carotid artery occlusion (15 min) alone or with release (15 and 60 min) served as a model for edema induction. NLA, N omega-nitro-D-arginine methyl ester (D-NAME) or Ringer's solution were administered 4 hr prior to ischemia or sham operation. Treatment with a stable nitroxide radical, 4-hydroxy-2,2, 6,6-tetramethylpiperidine-L-oxyl (TPL), was used to assess free radical involvement in edema. Accumulation of tissue water was evaluated by measuring specific gravity (SG) of brain cortex and histological examination. There was a greater reduction of cortical SG in early reperfusion (15 min) and a lesser decrease in SG (60 min later) in NLA-than in D-NAME- or Ringer's-treated gerbils. The NLA effect was confirmed by histological examination of the brain tissue. TPL treatment (pre- and postischemic) ameliorated the formation of edema to the same degree as NLA. The findings indicate a biphasic NLA modulation of cytotoxic edema most likely mediated through absence or presence of NO-derived free radicals.

Topics: Animals; Brain Edema; Brain Ischemia; Enzyme Inhibitors; Female; Gerbillinae; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine

To ascertain whether complete cerebral ischemia-reperfusion activate L-Arg: NO pathway in canine brain, we anestherized nine adult dogs with ketamine and fentayle and randomly divided into two groups. Four dogs were nonischemic control group. Five dogs were complete cerebral ischemia-reperfusion group, they underwent a 18-minute cardiac arrest, and were resusciatation by standard CPR, supported by intensive care for 8 hours. At the end of each experiment, the parietal cortex was assayed for content of Nitrite and NADPH-positive neurons. Compared with the control group, the contents of Nitrite and NADPH-positive neurons of coxtex in complete cerebral ischemia-reperfusion group increased significantly (P < 0.01). The results suggest that complete cerebral ischemia-reperfusion activate the L-Arg: NO pathway in canine brain, and NO may play an important role in cerebral ischemia-reperfusion injury.

Topics: Animals; Brain Ischemia; Dogs; Nitric Oxide; Nitroarginine; Random Allocation; Reperfusion Injury

Tissue nitric oxide (NO) concentration was investigated in relation to ion-homeostasis disturbance in the cat model of focal cerebral ischaemia. An NO electrode, a Ca2+ microelectrode and a laser Doppler probe were applied to the cerebral cortex in the core and periphery of the middle cerebral artery. NO concentration increased by 25.1 +/- 6.3 nM at 5 min in severely ischaemic regions exhibiting anoxic depolarization (n = 5, p < 0.0005). This occurred with no reduction in extracellular Ca2+ concentration and before a massive Ca2+ influx into cells started several minutes later. The NO increase was abolished by NG-nitro-L-arginine treatment (n = 6, p < 0.05) and was absent in regions with no depolarization (n = 5, p < 0.0005). We conclude that the early increase in NO associated with depolarization is achieved by activation of constitutive NO synthase, possibly triggered by intracellular Ca2+ release.

Topics: Acute Disease; Animals; Biosensing Techniques; Blood Pressure; Body Temperature; Brain Ischemia; Calcium; Cats; Cerebrovascular Circulation; Electrophysiology; Enzyme Inhibitors; Extracellular Space; Female; Hypoxia, Brain; Laser-Doppler Flowmetry; Microelectrodes; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine

The effect of nitro-L-arginine (NLA), inhibitor of NO synthase, on ET-1 content in cerebrospinal fluid (CSF) and on the vascular system was investigated in global ischemia/reperfusion of Mongolian gerbils. The results indicate that NLA induced a prolonged (2-3-fold) increase of ET-1 concentration above that seen in the CSF of untreated animals during ischemia/reperfusion. Both the transient and prolonged rise of ET-1 content observed in the CSF coincided with the reduction in the cerebral blood flow seen in untreated and NLA-treated gerbils, respectively, at the time of reperfusion.

Topics: Animals; Arginine; Brain Ischemia; Cerebrovascular Circulation; Endothelins; Enzyme Inhibitors; Gerbillinae; Nitroarginine; Osmolar Concentration; Reperfusion; Time Factors

The present study was designed to determine the effect of nitro-L-arginine, the inhibitor of nitric oxide synthesis, on the evolution of cytotoxic brain edema during focal cerebral ischemia.. Diffusion-weighted and contrast-enhanced, perfusion-sensitive magnetic resonance imaging was performed in anesthetized, mechanically ventilated rats at 30 minutes and 1, 2, and 3 hours after occlusion of the middle cerebral artery combined with coagulation of the basilar artery. At the onset of ischemia, the animals were infused intravenously with 0.5 mL of either 0.9% NaCl or nitro-L-arginine (30 mg/kg). The severity of cytotoxic edema was evaluated based on changes in the water apparent diffusion coefficient (ADC) derived from diffusion-weighted images. The size of the area affected by ischemia was evaluated 3 hours after occlusion using 2,3,5-triphenyltetrazolium chloride (TTC) staining.. The percentage decrease of ADC in the striatum of rats pretreated with nitro-L-arginine was significantly smaller (P < .05) than in the control group at 30 minutes and 1 and 2 hours of ischemia. The ADC in the injured cortex of nitro-L-arginine-treated rats did not differ significantly from the ADC value measured in the contralateral cortex until 3 hours after the occlusion. However, at 3 hours of ischemia the percentage decrease of ADC in both the striatum and the cortex of either group of rats was similar. This transient attenuation of ADC drop during ischemia after nitro-L-arginine pretreatment occurred concurrently with a transient improvement of blood supply to the ischemic regions. The percentage of hemispheric area with abnormal TTC staining after 3 hours of ischemia did not differ between control and nitro-L-arginine-treated rats.. Nitro-L-arginine delays the development of ischemic injury by retarding cytotoxic brain edema. This effect is, at least partially, mediated by an improvement in blood supply to the ischemia tissues.

Topics: Animals; Arginine; Brain Edema; Brain Ischemia; Cerebral Cortex; Corpus Striatum; Hemodynamics; Male; Nitric Oxide; Nitroarginine; Rats; Rats, Sprague-Dawley

To elucidate the mechanisms of ischemic cell damage, biochemical disturbances developing during and following in vitro ischemia of 5, 10 or 15 min duration were compared in hippocampal slices prepared from gerbil and rat brains. During ischemia the release of glutamate from slices into the medium was determined, and after ischaemia and 10 min of recovery slices were analyzed for ATP levels, adenylate energy charge and cGMP content. The release of glutamate into the medium during in vitro ischemia and the recovery of energy metabolism determined after 10 min of recovery was almost identical in slices prepared from gerbil and rat hippocampi. In contrast, cGMP levels measured 10 min following in vitro ischemia were significantly higher in gerbil as compared to rat slices. Since after 10 min of recovery following in vitro ischemia, cGMP levels reflect nitric oxide (NO) synthesis (inhibition by NO synthase blocker), it is concluded that increased NO synthesis may contribute to the higher sensitivity of the gerbil as compared to the rat hippocampus towards transient ischemia.

Topics: Adenosine Triphosphate; Animals; Arginine; Brain Ischemia; Cyclic GMP; Energy Metabolism; Enzyme Inhibitors; Gerbillinae; Glutamic Acid; Hippocampus; In Vitro Techniques; Male; Nitric Oxide Synthase; Nitroarginine; Rats

We performed experiments to investigate the participation of nitric oxide (NO) in the delayed neuronal death (DND) of gerbil hippocampal CA1 neurons, following 5-min forebrain ischemia with pretreatment of stereotaxic intraventricular administration of several types of NO synthase inhibitors and biologically inactive control drugs. The number of surviving neurons in the control drug groups administered NG-monomethyl-D-arginine or NG-nitro-D-arginine methyl ester was comparable to that in the group administered artificial cerebro-spinal fluid, while the groups administered NOS inhibitors, such as NG-monomethyl-L-arginine or NG-nitro-L-arginine methyl ester, showed significant preservation of the neuronal densities compared with the control drug groups, to over 60% of the sham operation group value. Furthermore, intraventricular administration of N omega-nitro-L-arginine at various concentrations disclosed a dose-dependent protection against the DND. These results suggest that the generation of NO may act to promote the establishment of DND.

Topics: Animals; Arginine; Brain Ischemia; Cell Death; Enzyme Inhibitors; Gerbillinae; Hippocampus; Injections, Intraventricular; Male; Neurons; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine

Topics: Amino Acid Oxidoreductases; Animals; Arachidonic Acid; Arginine; Brain; Brain Ischemia; Cyclic GMP; Gerbillinae; Glutamates; Male; Membrane Lipids; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Receptors, N-Methyl-D-Aspartate; Signal Transduction

The neuroprotective effects of various doses of N omega-nitro-L-arginine have been correlated with the degree of N omega-nitro-L-arginine-induced inhibition of cortical nitric oxide synthase activity measured ex vivo. Following focal cerebral ischemia induced by permanent occlusion of middle cerebral artery in the mouse, repeated administration of 1 mg/kg i.p. of N omega-nitro-L-arginine (beginning 5 min after surgery) reproducibly decreased by 66-76% the infarct volume measured at 6 days post-occlusion. This dose of N omega-nitro-L-arginine decreased cortical nitric oxide (NO) synthase activity by 70-73%. The neuroprotective efficacy of N omega-nitro-L-arginine increased dose-dependently over the range of doses of 0.1-1 mg/kg. Within this dose range of N omega-nitro-L-arginine, there was a good parallelism between the extent of inhibition of cortical NO synthase activity measured ex vivo and the degree of neuroprotection. However, higher doses of N omega-nitro-L-arginine (3 and 10 mg/kg i.p.), which inhibited NO synthase activity more effectively (up to 94%) failed to significantly reduce the infarct size. Repeated administrations of increasing doses of L-arginine (up to 30 mg/kg i.p.) with a low dose of N omega-nitro-L-arginine (1 mg/kg i.p.) caused a dose-dependent reduction in the neuroprotective efficacy of N omega-nitro-L-arginine while the extent of NO synthase inhibition measured ex vivo did not decrease significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Brain Ischemia; Cerebral Cortex; Cerebral Infarction; Dose-Response Relationship, Drug; Injections, Intraperitoneal; Male; Mice; Nitric Oxide Synthase; Nitroarginine

The proposal that nitric oxide (NO) or its reactant products mediate toxicity in brain remains controversial in part because of the use of nonselective agents that block NO formation in neuronal, glial, and vascular compartments. In mutant mice deficient in neuronal NO synthase (NOS) activity, infarct volumes decreased significantly 24 and 72 hours after middle cerebral artery occlusion, and the neurological deficits were less than those in normal mice. This result could not be accounted for by differences in blood flow or vascular anatomy. However, infarct size in the mutant became larger after endothelial NOS inhibition by nitro-L-arginine administration. Hence, neuronal NO production appears to exacerbate acute ischemic injury, whereas vascular NO protects after middle cerebral artery occlusion. The data emphasize the importance of developing selective inhibitors of the neuronal isoform.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Brain; Brain Ischemia; Cerebral Infarction; Cerebrovascular Circulation; Female; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Mutation; Neurons; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine

To assess the effects of the nitric oxide synthase inhibitor NG-Nitro-L-arginine on behavioural, biochemical and histological changes following global ischaemia, the Mongolian gerbil was used. Ischaemia was induced by bilateral carotid occlusion for 5 min. NG-Nitro-L-arginine was administered i.p. at either 1 or 10 mg/kg 30 min, 6, 24, and 48 h after surgery. 5 min bilateral carotid occluded animals were hyperactive 24, 48 and 72 h after surgery. NG-Nitro-L-arginine caused some attenuation in this hyperactivity. The activity of nitric oxide synthase was increased in the cerebellum, brain stem, striatum, cerebral cortex and hippocampus of 5 min bilateral carotid occluded animals. NG-Nitro-L-arginine reversed the increase in nitric oxide synthase activity in all brain regions. Extensive neuronal death was observed in the CA1 layer of the hippocampus in 5 min bilateral carotid occluded animals 96 h after surgery. NG-Nitro-L-arginine significantly protected against the neuronal death of cells in the CA1 layer.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Brain Ischemia; Brain Stem; Carotid Arteries; Cell Death; Cerebellum; Cerebral Cortex; Corpus Striatum; Disease Models, Animal; Gerbillinae; Hippocampus; Male; Microscopy, Fluorescence; Motor Activity; Neurons; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Paraffin Embedding; Reperfusion Injury

Inhibition of nitric oxide synthase with nitro-L-arginine (i.p., 40 mg/kg body weight) in contrast to L-arginine (300 mg/kg body weight) delayed the initial recovery of cerebral blood flow (CBF) and altered dopamine (DA) metabolism in brain ischemia/reperfusion of Mongolian gerbils. Similar changes but more severe were observed with pargyline (monoamine oxidase inhibitor). Data suggest nitric oxide involvement in postischemic CBF recovery and modulation of DA metabolism due to nitro-L-arginine-induced CBF reduction.

Topics: 3,4-Dihydroxyphenylacetic Acid; Analysis of Variance; Animals; Arginine; Biogenic Monoamines; Body Temperature; Brain Ischemia; Cerebrovascular Circulation; Female; Gerbillinae; Homovanillic Acid; Nitroarginine; Pargyline; Reperfusion Injury

We evaluated the neuroprotective effect of the nitric oxide synthesis inhibitor, NG-nitro-L-arginine in a neonatal hypoxic-ischemic rat model. Unilateral hypoxic-ischemic injury was produced in the brain of 7-d-old rats using a combination of a common carotid artery ligation and a hypoxic (8% oxygen) exposure for 2.5 h. In our experimental condition, rectal temperatures did not differ between NG-nitro-L-arginine-treated and saline-injected pups. We killed the animals 72 h later and assessed the hypoxic-ischemic brain damage histologically. NG-nitro-L-arginine (2 mg/kg) administered intraperitoneally 1.5 h before hypoxia resulted in 77% reduction of the infarcted hemispheric volume and 87% reduction of the infarcted striatal volume compared to saline injected controls. NG-nitro-L-arginine given 1.5 h before the insult also significantly prevented hypoxic-ischemic damage in the five hippocampal structures examined, dentate gyrus, CA4, CA3, CA1, and subiculum. NG-nitro-L-arginine administered immediately after hypoxia did not prevent hypoxic-ischemic brain damage. These results indicate that nitric oxide plays a key role in producing neonatal hypoxic-ischemic brain damage.

Topics: Animals; Animals, Newborn; Arginine; Brain Ischemia; Disease Models, Animal; Female; Hypoxia, Brain; Male; Nitric Oxide; Nitroarginine; Rats; Rats, Wistar; Time Factors

Recent evidence in primary neuronal cell culture implicates nitric oxide (NO) as a mediator of glutamatergic neurotoxicity acting via N-methyl-D-aspartate (NMDA) receptors. We find that administration of the potent nitric oxide synthetase (NOS) inhibitor NG-nitro-L-arginine (NO-Arg) at 50 mg/kg to 100 mg/kg i.p. to 6-day old Sprague-Dawley rat pups results in prompt and long-lasting in vivo inhibition of NOS. Fifteen hours after administration, NO-Arg produces essentially complete neuroprotection against hypoxic-ischemic in a standard (Rice-Vanucci) model. These results support the hypothesis that NO may play a key mediatory role in brain damage attending focal ischemic stroke.

Topics: Animals; Animals, Newborn; Arginine; Brain Ischemia; Nitric Oxide; Nitroarginine; Rats; Rats, Inbred Strains

In order to investigate whether or not nitric oxide (NO) formation underlies the cellular mechanisms of ischemic brain damage, we examined the effects of N omega-nitro-L-arginine (L-NNA), a NO synthase inhibitor, on ischemic brain edema and subsequent infarction in rats with middle cerebral artery occlusion (MCAo). For this purpose, administrations of L-NNA (1 mg/kg, i.p.) to each animal were done at the time of 5 min, 3, 6 and 24 h after MCAo, respectively. It was shown from this study that L-NNA significantly mitigated ischemic cerebral edema, and histological examinations revealed that this compound markedly reduced infarction size that occurred following MCAo. These results strongly suggest that NO formation is at least partly involved in the pathogenetic mechanisms of ischemic brain edema and subsequent cerebral infarction.

Topics: Animals; Arginine; Brain Chemistry; Brain Edema; Brain Ischemia; Cerebral Arteries; Cerebral Infarction; Male; Nitric Oxide; Nitroarginine; Potassium; Rats; Rats, Sprague-Dawley; Sodium

Endothelium-derived relaxing factor [EDRF, nitric oxide (NO) or a NO-containing compound] influences basal tone of cerebral blood vessels and mediates vasodilation in response to several stimuli. It is not known whether EDRF also modulates responses to cerebral vasoconstrictor stimuli in vivo. Our goal was to determine whether formation of EDRF inhibits constrictor responses of large cerebral arteries to serotonin. We measured cerebral blood flow (microspheres) and pial microvascular pressure (servo null) in anesthetized rabbits and calculated resistance of large cerebral arteries. Responses to an inhibitor of NO formation, NG-nitro-L-arginine (L-NNA, 3 mg/kg i.v.), were examined. L-NNA produced an increase in resistance of large arteries and total cerebral vascular resistance of approximately 15% (p less than 0.05 for both variables) and a small decrease in cerebral blood flow (35 +/- 9 vs. 32 +/- 7 ml min-1 100 g-1, mean +/- SD, p less than 0.05). Under control conditions, infusion of serotonin (10 micrograms kg-1 min-1, into the left atrium) produced an increase in resistance of large arteries. Following treatment with L-NNA, the change in resistance of large arteries in response to serotonin was increased more than twofold (0.20 +/- 0.17 vs. 0.43 +/- 0.21 mm Hg ml-1 min 100 g, p less than 0.05). In contrast, L-NNA did not alter the increase in resistance of large arteries during hypocapnia. L-arginine inhibited the effects of L-NNA on baseline cerebral vascular resistance and on responses of large arteries to serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arginine; Blood Pressure; Brain Ischemia; Cerebral Arteries; Disease Models, Animal; Homeostasis; Nitric Oxide; Nitroarginine; Rabbits; Regional Blood Flow; Serotonin; Serotonin Antagonists; Vasoconstriction