nitroarginine and Nerve-Degeneration

Methamphetamine (METH) belongs to Amphetamine-type stimulants, METH abusers are at high risk of neurodegenerative disorders, including Parkinson's disease (PD). However, there are still no effective treatments to METH-induced neurodegeneration because its mechanism remains unknown. In order to investigate METH's neurotoxic mechanism, we established an in vitro PD pathology model by exposing PC12 cells to METH. We found the expression of nitric oxide synthase (NOS), nitric oxide (NO) and α-synuclein (α-syn) was significantly increased after METH treatment for 24h, in addition, the aggregattion of α-syn and the S-nitrosylation of protein disulphideisomerase(PDI) were also obviously enhanced. When we exposed PC12 cells to the NOS inhibitor N-nitro-L-arginine(L-NNA) with METH together, the L-NNA obviously inhibited these changes induced by METH. While when we exposed PC12 cells to the precursor of NO L-Arginine together with METH, the L-Arginine resulted in the opposite effect compared to L-NNA. And when we knocked down the PDI gene, the L-NNA did not have this effect. Therefore, PDI plays a significant role in neurological disorders related to α-syn aggregation, and it suggests that PDI could be as a potential target to prevent METH-induced neurodegeneration.

Topics: alpha-Synuclein; Animals; Apoptosis; Cell Survival; Central Nervous System Stimulants; Enzyme Inhibitors; Gene Knockdown Techniques; Methamphetamine; Nerve Degeneration; Neurons; Neurotoxicity Syndromes; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; PC12 Cells; Protein Disulfide-Isomerases; Protein Processing, Post-Translational; Rats; RNA Interference; Time Factors; Transfection

NO synthesis disturbances play an important role in the development of neurodegenerative damage in Alzheimer disease. We previously showed that adaptation to intermittent hypobaric hypoxia prevents cognitive disturbances in rats with experimental Alzheimer disease. Here we evaluated the role of NO in cognitive disorders and development of adaptive protection during experimental Alzheimer disease. Adaptation to hypoxia in rats was performed in a hypobaric pressure chamber at a simulated altitude of 4000 m (4 h per day for 14 days). Alzheimer disease was simulated by bilateral injections of a toxic fragment of beta-amyloid (25-35) into n. basalis magnocellularis. For evaluation of the role of NO in the development and prevention of memory disorders, the rats received intraperitoneally either NO-synthase inhibitor N omega-nitro-L-arginin (L-NNA, 20 mg/kg, every other day for 14 days) or NO-donor dinitrosyl iron complex (200 microg/kg daily for 14 days). NO-synthase inhibitor potentiated the damaging effect of beta-amyloid, abolished the protective effect of adaptation to hypoxia, and produced memory disorders in rats similar to those observed during experimental Alzheimer disease. In contrast, the increase in NO level in the body provided by injections of the NO-donor produced a protective effect against memory disorders caused by beta-amyloid similar to that induced by adaptation to hypoxia. We concluded that reduced NO production in the organism plays an important role in the development of cognitive disorders produced by injections of beta-amyloid, while prevention of NO deficit by administration of NO-donors or non-pharmacological stimulation of NO synthesis can provide a protective effect in experimental Alzheimer disease.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Cognition Disorders; Hypoxia; Iron; Male; Nerve Degeneration; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Nitrogen Oxides; Peptide Fragments; Rats; Rats, Wistar

Previous studies have shown that poly (ADP-ribose) polymerase (PARP) and DNA polymerase beta, nuclear enzymes, are associated with cell replication and DNA repair. The present study tests the hypothesis that hypoxia results in increased PARP and DNA polymerase activity in cerebral cortical neuronal nuclei to repair the hypoxia-induced damage to genomic DNA. Studies were conducted in 13 anesthetized and ventilated newborn piglets (age 3-5 days) divided into normoxic (n=5) and hypoxic (n=8) groups. Hypoxia was induced by decreasing inspired oxygen from 21% to 7% for 60 min. Cerebral tissue hypoxia was documented biochemically by determining the tissue levels of ATP and phosphocreatine (PCr). Following isolation of the cortical neuronal nuclei, the activity of PARP and DNA polymerase beta was determined. During hypoxia, the tissue ATP level decreased by 73% from 4.12+/-0.67 micromol/g brain to 1.12+/-0.34 micromol/g brain, and PCr decreased by 78% from 4.14+/-0.68-0.90+/-0.20 micromol/g brain. In hypoxic neuronal nuclei, PARP activity significantly increased from 5.88+/-0.51 pmol NAD/mg protein/h in normoxic nuclei to 10.04+/-2.02 (P=0.001). PARP activity inversely correlated with tissue ATP (r=0.78) and PCr levels (r=0.81). Administration of N-nitro-L-arginine prior to hypoxia decreased the hypoxia-induced increase in PARP activity by 67%. Endogenous DNA polymerase beta activity increased from 0.96+/-0.13 in normoxic nuclei to 1.39+/-0.18 nmol/mg protein/h in hypoxic nuclei (P<0.005). DNA polymerase beta activity in the presence of exogenous template increased from 1.54+/-0.14 in the normoxic to 2.42+/-0.26 nmol/mg protein/h in the hypoxic group (P<0.005). DNA polymerase beta activity in the presence or absence of template inversely correlated with the tissue ATP (r=0.95 and 0.84, respectively) and PCr levels (r=0.93 and 0.77, respectively). These results demonstrate that the activity of PARP and DNA polymerase beta enzymes increase with the increase in degree of cerebral tissue hypoxia. Furthermore, the results demonstrate a direct correlation between the PARP and the DNA polymerase beta activity. We conclude that tissue hypoxia results in increased PARP and DNA polymerase beta activities indicating activation of DNA repair mechanisms that may result in potential neuronal recovery following hypoxia and the hypoxia-induced increase in PARP activity is NO-mediated.

Topics: Adenosine Triphosphate; Animals; Asphyxia Neonatorum; Cell Nucleus; Cerebral Cortex; DNA Damage; DNA Polymerase beta; DNA Repair; Enzyme Inhibitors; Humans; Hypoxia, Brain; Infant, Newborn; NAD; Nerve Degeneration; Neurons; Nitric Oxide; Nitroarginine; Phosphocreatine; Poly(ADP-ribose) Polymerases; Recovery of Function; Sus scrofa; Up-Regulation

The effect of lesions induced by bilateral intracerebroventricular (i.c.v.) injection of quinolinate (250 nmol of QUIN/ventricle), a selective N-methyl-D-aspartate (NMDA) receptor agonist, on [3H]glutamate ([3H]Glu) binding to the main types of both ionotropic and metabotropic glutamate receptors (iGluR and mGluR) was investigated in synaptic membrane preparations from the hippocampi of 50-day-old rats. The membranes from QUIN injured brains revealed significantly lowered binding in iGluR (by 31%) as well as in mGluR (by 22%) as compared to the controls. Using selected glutamate receptor agonists as displacers of [3H]Glu binding we found that both the NMDA-subtype of iGluR and group I of mGluR are involved in this decrease of binding. Suppression of nitric oxide (NO) production by N(G)-nitro-L-arginine (50 nmol of NARG/ventricle) or the increase of NO generation by 3-morpholinylsydnoneimine (5 nmol of SIN-1/ventricle) failed to alter [3H]Glu or [3H]CPP (3-((D)-2-carboxypiperazin-4-yl)-[1,2-(3)H]-propyl-1-phosphonic acid; NMDA-antagonist) binding declines caused by QUIN-lesions. Thus, our findings indicate that both the NMDA-subtype of iGluR and group I of mGluR are susceptible to the QUIN-induced neurodegeneration in the rat hippocampus. However, the inhibition of NO synthesis did not reveal any protective action in the QUIN-evoked, NMDA-receptor mediated decrease of [3H]Glu binding. Therefore, the additional mechanisms of QUIN action, different from direct NMDA receptor activation/NO production (e.g. lipid peroxidation induced by QUIN-Fe-complexes) cannot be excluded.

Topics: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; Animals; Binding, Competitive; Cell Membrane; Excitatory Amino Acid Agonists; Glutamic Acid; Hippocampus; Kainic Acid; Male; Molsidomine; N-Methylaspartate; Nerve Degeneration; Nitric Oxide Donors; Nitric Oxide Synthase; Nitroarginine; Quinolinic Acid; Quisqualic Acid; Rats; Rats, Wistar; Tritium

Autoradiography with [3H]nitro-L-arginine (3HL-NNA) was used to quantify nitric oxide synthase (NOS), and immunocytochemistry to identify NOS isoforms, in spinal cord in amyotrophic lateral sclerosis (ALS) and controls.. In controls NOS binding was marked only in the superficial dorsal horn, but in ALS tissue it was intense throughout the grey and white matter. A single population of binding sites was indicated in controls, but two populations in ALS. In the controls intense neuronal NOS (nNOS) immunoreactivity was present in numerous cells in the dorsal horn, and faint immunoreactivity in small and medium-sized cells in the ventral horn. Only weak immunoreactivity for inducible NOS (iNOS) and endothelial NOS (eNOS) was detectable in control tissue. In ALS, the pattern was broadly similar in the grey matter, but immunoreactivity for both nNOS and iNOS was present in white matter.. Expression of abnormal variants of nNOS or increased expression of iNOS may have a role in motoneuron death in ALS.

Topics: Aged; Aged, 80 and over; Amyotrophic Lateral Sclerosis; Autoradiography; Cell Count; Enzyme Inhibitors; Female; Humans; Immunohistochemistry; Male; Middle Aged; Motor Neurons; Nerve Degeneration; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; Nitroarginine; Spinal Cord; Tritium

Nitric oxide (NO) synthesized by inducible nitric oxide synthase (iNOS) has been implicated in neuronal cytotoxicity following trauma to the central nervous system. The aim of the present study was to examine the role of NO in mediating axotomy-induced retinal ganglion cell (RGC) death. We observed increases in iNOS expression by microglia and Müller cells in the retina after optic nerve transection. This was paralleled by the induced expression of constitutive NOS (cNOS) in RGCs which do not normally express this enzyme. In order to determine if NO is cytotoxic to axotomized RGCs, the nonspecific NOS inhibitors Nomega-nitro-L-arginine (NOLA) or N-nitro-L-arginine methyl ester (L-NAME) were delivered to the vitreous chamber by intraocular injections. Both NOLA and L-NAME significantly enhanced RGC survival at 7, 10, and 14 days postaxotomy. The separate contributions of iNOS and cNOS to RGC degeneration were examined with intraocular injections of the specific iNOS inhibitor L-N(6)-(I-iminoethyl)lysine hydrochloride or the specific cNOS inhibitor L-thiocitrulline. Our results suggest that cNOS plays a greater role in RGC degeneration than iNOS. In addition to enhancing RGC survival, NOS inhibitors delayed the retrograde degeneration of RGC axons after axotomy. We conclude that NO synthesized by retinal iNOS and cNOS plays a major role in RGC death and retrograde axonal degeneration following axotomy.

Topics: Animals; Axons; Axotomy; Cell Survival; Citrulline; Dihydrolipoamide Dehydrogenase; Enzyme Inhibitors; Female; Gene Expression Regulation, Enzymologic; Injections; Lysine; Nerve Degeneration; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitric Oxide Synthase Type II; Nitroarginine; Optic Nerve; Rats; Rats, Sprague-Dawley; Retinal Ganglion Cells; Thiourea; Time Factors

Senile plaques of Alzheimer's brain are characterized by activated microglia and immunoreactivity for the peptide chromogranin A. We have investigated the mechanisms by which chromogranin A activates microglia, producing modulators of neuronal survival. Primary cultures of rat brain-derived microglia display a reactive phenotype within 24 h of exposure to 10 nM chromogranin A, culminating in microglial death via apoptotic mechanisms mediated by interleukin-1beta converting enzyme. The signalling cascade initiated by chromogranin A triggers nitric oxide production followed by enhanced microglial glutamate release, inhibition of which prevents microglial death. The plasma membrane carrier inhibitor aminoadipate and the type II/III metabotropic glutamate receptor antagonist (RS)-alpha-methyl-4-sulphonophenylglycine are equally protective. A significant amount of the released glutamate occurs from bafilomycin-sensitive stores, suggesting a vesicular mode of release. Inhibition of this component of release affords significant microglial protection. Conditioned medium from activated microglia kills cerebellar granule cells by inducing caspase-3-dependent neuronal apoptosis. Brain-derived neurotrophic factor is partially neuroprotective, as are ionotropic glutamate receptor antagonists, and, when combined with boiling of conditioned medium, full protection is achieved; nitric oxide synthase inhibitors are ineffective.

Topics: Alzheimer Disease; Animals; Apoptosis; Biomarkers; Caspase 1; Caspase 3; Caspase Inhibitors; Caspases; Cell Size; Cells, Cultured; Cerebellum; Chromogranin A; Chromogranins; Enzyme Inhibitors; Glial Fibrillary Acidic Protein; Glutamic Acid; Macrophages; Microglia; Nerve Degeneration; Neurons; Neurotoxins; Nitric Oxide; Nitroarginine; Oligopeptides; Rats

The role of nitric oxide (NO) in the long-term serotoninergic neurotoxicity induced by (+/-)3,4-methylenedioxymethamphetamine (MDMA) in rats was investigiated. Pretreatment with Nomega-nitro-L-arginine (L-NOARG) (10 mg kg-1), a nitric oxide synthase (NOS) inhibitor, partially protected against long-term serotonin (5-HT) depletion induced by MDMA (40 mg kg-1) in frontal cortex and parietal cortex, but not in other brain regions examined. Brain NOS activities in these two regions were significantly elevated at 6 h after MDMA administration. Moreover, L-NOARG pretreatment caused significant inhibition of brain NOS activity but did not affect the acute 5-HT and dopamine (DA) changes or the hyperthermia induced by MDMA. These results suggest that it is the NOS inhibitory properties of L-NOARG, rather than its effects on the acute monoamine changes or the hyperthermia induced by MDMA, that are responsible for the prevention of neurotoxicity. The regional differences on the protection of L-NOARG and on the activation of NOS by MDMA indicate the unequal role that NO may play in MDMA-induced neurotoxicity in different brain regions.

Topics: Animals; Body Temperature; Enzyme Activation; Enzyme Inhibitors; Hydroxyindoleacetic Acid; Indazoles; Male; N-Methyl-3,4-methylenedioxyamphetamine; Nerve Degeneration; Nerve Tissue Proteins; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type I; Nitroarginine; Rats; Rats, Sprague-Dawley; Serotonin; Serotonin Agents

Previously, we have reported that intranigral infusions of malonate, an inhibitor of mitochondrial function, lead to the degeneration of the dopaminergic neurons of the nigrostriatal pathway that is mediated, at least in part, through NMDA receptor activation and nitric oxide formation. In the present study, unilateral focal infusions of malonate into the nucleus basalis magnocellularis (nbM) of male Sprague-Dawley rats (weighing 250-300 g) resulted in a dose-related depletion in ipsilateral cortical and amygdaloid choline acetyltransferase (ChAT) activity. Infusion of a 3 mumol dose of malonate into the nbM of vehicle-treated animals resulted in a 41 and 54% decrease in cortical and amygdaloid ChAT activity, respectively. Systemic pretreatment with lamotrigine (16 mg/kg, i.p.) and MK-801 (5 mg/kg, i.p.) attenuated the depletions in cortical and amygdaloid ChAT activity that resulted from an infusion of this dose of malonate into the nbM. Acetylcholinesterase (AChE) histochemistry of the nbM following focal infusion of malonate (3 mumol) showed a marked decrease in the number of AChE-positive neurons that was partially prevented by MK-801 pretreatment. Before examining the role of nitric oxide formation in malonate-induced toxicity, the ability of systemic administration of N omega-nitro-L-arginine (L-NA) to inhibit nitric oxide synthase (NOS) activity in the nbM and cerebellum was investigated. L-NA (2, 10, and 20 mg/kg, i.p.) produced a dose-related inhibition of nbM and cerebellar NOS activity that was maximal following a dose of 10 mg/kg L-NA. This level of NOS inhibition persisted for at least 13 h following L-NA (10 mg/kg) administration. Subsequently, the effect of L-NA pretreatment on malonate toxicity was evaluated. Following pretreatment with L-NA (2 and 10 mg/kg, i.p.), the toxic action of malonate on cortical and amygdaloid ChAT activity was not altered. In addition, infusion of a lower dose of malonate (2 mumol) into the nbM resulted in decreases in cortical and amygdaloid ChAT activity that were not altered by pretreatment with L-NA (2 and 10 mg/kg, i.p.). In 7-nitroindazole (7-NI; 25 and 50 mg/kg, i.p.)-pretreated animals, malonate (3 mumol) produced decreases in cortical and amygdaloid ChAT activity that were attenuated by both doses of 7-NI. Thus, malonate-induced destruction of the basal forebrain cholinergic neurons was attenuated by systemic pretreatment with lamotrigine, MK-801, and 7-NI but not by L-NA.

Topics: Animals; Dizocilpine Maleate; Enzyme Inhibitors; Indazoles; Lamotrigine; Male; Malonates; Nerve Degeneration; Neurons; Neuroprotective Agents; Nitric Oxide Synthase; Nitroarginine; Parasympathetic Nervous System; Prosencephalon; Rats; Rats, Sprague-Dawley; Triazines

Nitric oxide, a simple gas which serves as a neurotransmitter in the CNS, has been proposed to serve as an interneuronal second messenger in olfactory transduction. However, the role of nitric oxide in olfaction has been questioned by experiments in which nitric oxide synthase, the enzyme that generates nitric oxide, could not be localized to the olfactory epithelium. We have localized nitric oxide synthase to the olfactory neurons in adult rat and catfish olfactory epithelia using a modified nicotinamide adenine dinucleotide phosphate diaphorase technique. In the rat, staining was also found in cells with morphology reminiscent of microvillar olfactory cells. In contrast, the respiratory epithelium and the sustentacular cells in the olfactory epithelium displayed no staining. The nicotinamide adenine dinucleotide phosphate diaphorase reaction, which has been shown to co-localize with immunohistochemical staining for nitric oxide synthase in the brain, was stimulated by addition of the nitric oxide synthase substrate L-arginine, and was inhibited by the nitric oxide synthase inhibitor L-NG-nitro arginine, indicating that staining was specific for nitric oxide synthase. Unilateral bulbectomy, which causes degeneration of mature olfactory neurons on the bulbectomized size, markedly reduced nicotinamide adenine dinucleotide phosphate diaphorase staining. These observations were substantiated by biochemical assays for nitric oxide synthase by monitoring the production of [3H]-L-citrulline from [3H]-L-arginine. This is the first demonstration of specific NADPH diaphorase staining of mature olfactory neurons in rat and catfish olfactory epithelial suggesting the presence of nitric oxide synthase in these cells. Our histological and biochemical findings, in conjunction with data from other research, are supportive of a role for nitric oxide synthase in olfactory function.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Cilia; Female; Histocytochemistry; Ictaluridae; NADPH Dehydrogenase; Nerve Degeneration; Neurons, Afferent; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Olfactory Bulb; Olfactory Mucosa; Rats; Rats, Sprague-Dawley; Smell; Species Specificity

Nitrix oxide (NO) is a free radical that has been recently proposed as a messenger molecule in the central nervous system. Since its involvement in glutamate neurotoxicity in vitro has been recently reported, using rat cortical cultures, we tested the hypothesis that NO also plays a role in neuronal injury induced by deprivation of oxygen and glucose. About 80-90% of neurons were killed in less than 12 h after a 4-6 h period of oxygen and glucose deprivation. N-nitro-L-arginine (L-NNA), an inhibitor of nitric oxidase synthase (NOS), significantly ameliorated this neuronal injury in a dose dependent manner. Since it has been suggested that NO is inactivated in a short time period by interaction with superoxide anions (O2-), which are generated during ischemia-reperfusion in vivo, we further evaluated the effect of superoxide dismutase (SOD) on neuronal injury in this test system. SOD failed, however, to protect against neuronal death. Furthermore, concomitant addition of SOD and L-NNA rather reduced the beneficial effects of L-NNA. Our results suggest therefore that NO, at least in part, mediates neuronal injury secondary to deprivation of oxygen and glucose in vitro and that superoxide anions may have a protective role by inactivating NO.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Blood Glucose; Cell Hypoxia; Cell Survival; Cerebral Cortex; Culture Techniques; Free Radicals; Nerve Degeneration; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Reactive Oxygen Species; Superoxide Dismutase

Nitric oxide (NO) is a potent biological messenger molecule in the central nervous system (CNS). There are several potential sources of NO production in the CNS, including neurons and endothelial cells which express NO synthase (NOS) constitutively. Astrocytes and microglia can be induced by cytokines to express a NOS isoform similar to macrophage NOS (mNOS). Primary mixed glial cultures exposed to lipopolysaccharide (LPS) or a combination of LPS and gamma-interferon (INF-gamma) produce nitrite, a breakdown product of NO formation, in a dose-dependent manner. Nitrite production is detectable at 12 hr, peaks at 48 hr and is sustained for at least 96 hr. The NOS inhibitor, nitro-L-arginine (NArg), inhibits nitrite formation, but the immunosuppressant agent, FK506, does not. In mixed glial-neuronal cultures exposed to 50 ng LPS or 5 ng LPS and 1 microgram INF-gamma, neurons begin to die at 48 hr, approx. 24-36 hr after detectable nitrite production. Neurotoxicity is attenuated by 100 microM NArg. These data indicate that expression of inducible mNOS causes delayed neurotoxicity.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Cells, Cultured; Cerebral Cortex; Interferon-gamma; Lipopolysaccharides; Nerve Degeneration; Nervous System Diseases; Neuroglia; Neurons; Nitric Oxide Synthase; Nitrites; Nitroarginine; Rats; Tacrolimus

Nitric oxide (NO), generated upon glutamate receptor activation, elicits cyclic GMP accumulation through stimulation of guanylyl cyclase. NO is also a potential cytotoxin that has been suggested, on the basis of tissue culture experiments, to mediate neuronal damage associated with excessive activity of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor. We have investigated the involvement of NO in the toxicity of glutamate receptor agonists in brain slice preparations. Slices of cerebellum and hippocampus from the developing rat exhibited neuronal necrosis following exposure (5-30 min) to NMDA (100 microM or 1 mM). When the exposures were carried out in the presence of NO synthase inhibitors, at concentrations suppressing NMDA-induced NO formation (as judged by measurements of cyclic GMP accumulation), the extent of injury was unaffected. To determine if exogenous NO is able to replicate NMDA toxicity, the slices were exposed to high concentrations of NO donating compounds for up to 2 hr. No damage was detectable. NO donors, moreover, neither reduced NMDA toxicity, nor potentiated the degeneration caused by just suprathreshold NMDA concentrations. The toxicities of non-NMDA agonists, or of glutamate itself, were also unaltered by NO synthase inhibitors or NO donors. Similar results were obtained using hippocampal slices from more mature animals. We conclude that the acute neurodegeneration mediated by NMDA or non-NMDA receptors in the slice preparations is not mediated by NO, nor is NO neuroprotective under these conditions.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Cerebellum; Excitatory Amino Acids; Glutamic Acid; Hippocampus; In Vitro Techniques; N-Methylaspartate; Nerve Degeneration; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Wistar

In the presence of physiological concentrations of Mg2+ and in glycine-free buffer, the relationship between KA-mediated generation of NO and neurotoxicity in cultures of cerebellar granule cells of the rat was examined. The neuronal damage elicited by KA was not dependent on the presence of L-arginine, a precursor of NO, since neither the potency nor magnitude of KA-mediated cell death was altered in either the absence or presence of exogenously applied L-arginine. Similarly, with the exception of 4-hydroxy-azobenzene-4'-sulfonic acid, disodium salt dihydrate (HBS), the salt associated with NG-monomethyl-L-arginine (di-(p-hydroxyazobenzene-p'-sulfonate) (MA(HBS)), treatment with several different competitive NO synthetase inhibitors did not provide protection against the toxicity of KA. However, the ability of KA to induce neuronal damage was significantly decreased in cerebellar granule cells treated with either HBS or alpha-tocopherol (VE). On the basis of these results, it is concluded that the generation of free radicals may be involved in the process of KA-elicited neuronal death in cultures of cerebellar granule cells but that this is unrelated to the synthesis of NO. This conclusion agrees with both in vivo and in vitro studies, implicating the involvement of free radicals in non-NMDA mediated neuronal damage.

Topics: Animals; Arginine; Azo Compounds; Cell Death; Cells, Cultured; Cerebellum; Cyclic GMP; Kainic Acid; Kinetics; Magnesium; Nerve Degeneration; Neurons; Nitric Oxide; Nitroarginine; Rats; Rats, Wistar

To investigate whether nitric oxide (NO) plays a role in the neurotoxicity produced by N-methyl-D-aspartate (NMDA) we have examined the effects of NO inhibitors on NMDA-mediated neurodegeneration in the CA1 region of rat hippocampal slices. L-NG-Monomethylarginine, L-NG-nitroarginine and hemoglobin markedly diminished the toxicity produced by activation of NMDA receptors without interfering with NMDA receptor-mediated ion currents or synaptic responses. The neuroprotective effects are reversed by coapplication of L-arginine with the NO synthase inhibitors. These results suggest that activation of the NO system is an important component of the biochemical cascade leading to neurodegeneration produced by NMDA receptors.

Topics: Animals; Arginine; Calcium; Hemoglobins; Hippocampus; In Vitro Techniques; N-Methylaspartate; Nerve Degeneration; Nitric Oxide; Nitroarginine; omega-N-Methylarginine; Rats; Synapses