Neuroprotective effect of lamotrigine and MK-801 on rat brain lesions induced by 3-nitropropionic acid: evaluation by magnetic resonance imaging and in vivo proton magnetic resonance spectroscopy

Performance of the prospective T2 MRI biomarker of neurotoxicity in a trimethyltin model in rats at 7 T

The assessment of the sensitivity and specificity of any potential biomarker against the gold standard is an important step in the process of its qualification by regulatory authorities. Such qualification is an important step towards incorporating the biomarker into the panel of tools available for drug development. In the current study we analyzed the sensitivity and specificity of T2 MRI relaxometry to detect trimethyltin-induced neurotoxicity in rats. Seventy-five male Sprague-Dawley rats were injected with a single intraperitoneal dose of either TMT (8, 10, 11, or 12 mg/kg) or saline (2 ml/kg) and imaged with 7 T MRI before and 3, 7, 14, and 21 days after injection using a quantitative T2 mapping. Neurohistopathology (the gold standard in the case of neurotoxicity) was performed at the end of the observation and used as an outcome qualifier in receiver-operator characteristic (ROC) curve analysis of T2 changes as a predictor of neurotoxicity. TMT treatment led to a significant increase in T2 values in many brain areas. The biggest changes in T2 values were seen around the lateral ventricles, which was interpreted as ventricular dilation. The area under the ROC curve for the volume of the lateral ventricles was 0.878 with the optimal sensitivity/specificity of 0.805/0.933, respectively. T2 MRI is a promising method for generating a non-invasive biomarkers of neurotoxicity, which shows the dose-response behavior with substantial sensitivity and specificity. While its performance was strong in the TMT model, further characterization of the sensitivity and specificity of T2 MRI with other neurotoxicants is warranted.

Outcome of epilepsy in patients with mitochondrial disorders: Phenotype genotype and magnetic resonance imaging correlations

OBJECTIVES

Studies exploring the outcome of epilepsy in patients with mitochondrial disorders are limited. This study examined the outcome of epilepsy in patients with mitochondrial disorders and its relation with the clinical phenotype, genotype and magnetic resonance imaging findings.

PATIENTS AND METHODS

The cohort was derived from the database of 67 patients with definite genetic diagnosis of mitochondrial disorders evaluated over a period of 11years (2006-2016). Among this, 27 had epilepsy and were included in final analysis. Data were analyzed with special reference to clinical phenotypes, genotypes, epilepsy characteristics, EEG findings, anti epileptic drugs used, therapeutic response, and magnetic resonance imaging findings. Patients were divided into three groups according to the seizure frequency at the time of last follow up: Group I- Seizure free; Group II- Infrequent seizures; Group III- uncontrolled seizures. For each group the clinical phenotype, genotype, magnetic resonance imaging and duration of epilepsy were compared.

RESULTS

The phenotypes & genotypes included Mitochondrial Encephalopathy Lactic Acidosis and Stroke like episodes (MELAS) & m.3243A>G mutation (n = 10), Myoclonic Epilepsy Ragged Red Fiber syndrome (MERRF) & m.8344A>G mutation (n = 4), Chronic Progressive External Ophthalmoplegia plus &POLG1 mutation (CPEO, n = 6), episodic neuroregression due to nuclear mutations (n = 6; NDUFV1 (n = 3), NDUFA1, NDUFS2, MPV17-1 one each), and one patient with infantile basal ganglia stroke syndrome, mineralizing angiopathy &MT-ND5 mutations. Seven patients (25.9%) were seizure free; seven had infrequent seizures (25.9%), while thirteen (48.1%) had frequent uncontrolled seizures. Majority of the subjects in seizure free group had episodic neuroregression & leukoencephalopathy due to nuclear mutations (85.7%). Patients in group II with infrequent seizures had CPEO, POLG1 mutation and a normal MRI (71%) while 62% of the subjects in group III had MELAS, m.3243A>G mutation and stroke like lesions on MRI.

CONCLUSIONS

A fair correlation exists between the outcome of epilepsy, clinical phenotypes, genotypes and magnetic resonance imaging findings in patients with mitochondrial disorders. The recognition of these patterns is important clinically because of the therapeutic and prognostic implications.

Efficacy of Retigabine on Acute Limbic Seizures in Adult Rats

Background and Purpose:

The efficacy of retigabine (RGB), a positive allosteric modulator of K+ channels indicated for adjunct treatment of partial seizures, was studied in two adult models of kainic acid (KA)-induced status epilepticus to determine it’s toleratbility.

Methods:

Retigabine was administered systemiclly at high (5 mg/kg) and low (1–2 mg/kg) doses either 30 min prior to or 2 hr after KA-induced status epilepticus. High (1 µg/µL) and low (0.25 µg/µL) concentrations of RGB were also delivered by intrahippocampal microinjection in the presence of KA.

Results:

Dose-dependent effects of RGB were observed with both models. Lower doses increased seizure behavior latency and reduced the number of single spikes and synchronized burst events in the electroencephalogram (EEG). Higher doses worsened seizure behavior, produced severe ataxia, and increased spiking activity. Animals treated with RGB that were resistant to seizures did not exhibit significant injury or loss in GluR1 expression; however if stage 5–6 seizures were reached, typical hippocampal injury and depletion of GluR1 subunit protein in vulernable pyramidal fields occurred.

Conclusions:

RGB was neuroprotective only if seizures were significantly attenuated. GluR1 was simultaneously suppressed in the resistant granule cell layer in presence of RGB which may weaken excitatory transmission. Biphasic effects observed herein suggest that the human dosage must be carefully scrutinized to produce the optimal clinical response.

Alterations of cerebral glutamate in the euthymic state of patients with bipolar disorder

The pathophysiology of bipolar disorder (BD) mostly remains unclear. However, some findings argue for a dysfunction in glutamatergic neurotransmission in BD. Proton magnetic resonance spectroscopy at 3T was used to determine glutamate concentrations in the anterior cingulate cortex (ACC) and the hippocampus (HC) of euthymic outpatients with BP-I disorder and age- and sex-matched healthy controls. In patients with BD, glutamate concentrations were significantly increased in the ACC and decreased in the HC compared with concentrations in controls. Significant group differences were also measured for N-acetyl aspartate and choline; no differences were found for other metabolites examined. An inverse correlation was observed for glutamate concentrations in the ACC and number of episodes. The findings of the study add to the concept of abnormalities in glutamatergic regulation in the ACC and HC in patients with BD.

A rat model of hemidystonia induced by 3-nitropropionic acid

OBJECTIVE

Secondary dystonia commonly presents as hemidystonia and is often refractory to current treatments. We aimed to establish an inducible rat model of hemidystonia utilizing 3-nitropropionic acid (3-NP) and to determine the pathophysiology of this model.

METHODS

Two different doses of 3-NP were stereotactically administered into the ipsilateral caudate putamen (CPu) of Wistar rats. Behavioral changes and alterations in the neurotransmitter levels in the basal ganglia were analyzed. We also performed an electromyogram, 7.0-T magnetic resonance imaging and transmission electron microscopy examination to determine the pathophysiology of the model.

RESULTS

In the CPu region, 3-NP produced mitochondrial cristae rupture, axonal degeneration, increased excitatory synaptic vesicles and necrosis. The extracellular concentrations of excitatory amino acids increased, whereas the inhibitory amino acids decreased in the CPu. Furthermore, an imbalance of neurotransmitters was found in other regions of the basal ganglia with the exception of the external globus pallidus. This study demonstrated that 3-NP administration results in CPu damage, and combined with a neurotransmitter imbalance in the basal ganglia, it produces specific neurobehavioral changes in rats. Right limb (contralateral side of CPu lesion) and trunk dystonic postures, shortened step length and ipsiversive dystonic posturing were observed in these rats. Furthermore, EMG recordings confirmed that co-contraction of the agonist and antagonist muscles could be seen for several seconds in right limbs.

CONCLUSIONS

Stereotactic injection of 3-NP into the ipsilateral CPu of rats established an inducible model for hemidystonia. This effect might result from an imbalance of neurotransmitter levels, which induce dysfunctional activity of the basal ganglia mainly via the cortico-striato-GPi direct pathway. Symptoms in this model were present for 1 week. Activation of the cortico-striato-GPe indirect pathway and rebalance of neurotransmitters may lead to recovery. This rat model may be a suitable tool used to understand and further investigate the pathophysiology of dystonia.

Mitochondrial disease and epilepsy

Mitochondrial diseases are a group of diseases caused by dysfunctional mitochondria, organelles that generate energy for the cell. Mitochondrial diseases are often caused by mutations, acquired, or inherited in the mitochondrial DNA or nuclear genes that code for respiratory chain complexes in the mitochondrion. Mitochondrial diseases involve multiple organs and show heterogeneous and unpredictable progression. The most common clinical presentation of mitochondrial diseases is encephalomyopathy, and epileptic seizures can frequently occur as a presenting sign of mitochondrial encephalopathy. While whether mitochondrial dysfunction or epilepsy is the cause or consequence is still debatable, they may be interrelated to create a vicious cycle. Epileptic phenotypes vary in different mitochondrial diseases. At present, there are no curative treatments for mitochondrial diseases, and the efficacy of many anticonvulsants, vitamins, nutritional supplements, and the ketogenic diet remain to be proven. Understanding the pathophysiology of mitochondrial diseases may further facilitate effective diagnostic and therapeutic approaches to these diseases.

Mitochondrial diseases and epilepsy

The mitochondrial respiratory chain is the final common pathway for energy production. Defects affecting this pathway can give rise to disease that presents at any age and affects any tissue. However, irrespective of genetic defect, epilepsy is common and there is a significant risk of status epilepticus. This review summarizes our current understanding of the epilepsy that occurs in mitochondrial disease, focusing on three of the most common disorders: mitochondrial myopathy encephalopathy, lactic acidosis and stroke-like episodes (MELAS), myoclonus epilepsy and ragged-red fibers (MERRF), and polymerase gamma (POLG) related disease. In addition, we review the pathogenesis and possible treatment of these disorders.

Neuroprotective effect of naringin, a dietary flavonoid against 3-nitropropionic acid-induced neuronal apoptosis

The aim of this study was to investigate the protective effect of naringin, a flavonoid on 3-Nitropropionic acid (3-NP)-induced neurodegeneration through the modulation of intrinsic apoptotic cascade in Wistar rats. 3-NP is an irreversible inhibitor of complex II in the mitochondria. 3-NP-induced neurodegeneration has been widely used as an animal model of Huntington's disease (HD). Increased oxidative stress is one of the major deleterious events in 3-NP-induced neuronal apoptosis. Rats administered with 3-NP showed increase in the levels of lipid peroxidation and protein carbonyl, which was significantly decreased upon naringin treatment (80 mg/kg body weight). 3-NP-induced rats showed decrease in the activities of enzymic antioxidants and reduced levels of non-enzymic antioxidants. Naringin treatment ameliorated the antioxidant status by increasing the activities of enzymic antioxidants and the levels of non-enzymatic antioxidants. 3-NP-induced rats showed decrease in the activities of ATPases in striatum, which was restored to normal level upon naringin treatment. Histopathological observation of the striatal tissue showed protective role of naringin in 3-NP-induced rats. Naringin also reduced the 3-NP-induced apoptosis via decrease in the cytochrome c release from mitochondria and caspase 3 activation as revealed by Western blot. Naringin treatment also decreased the expressions of pro-apoptotic markers like Bad and Bax. Further, naringin antagonized 3-NP-induced decrease in Bcl-2 mRNA expression. The results of this study show evidence on the neuroprotective effect of naringin against 3-NP-induced neuronal apoptosis through its antioxidant and anti-apoptotic effects.

Neuroprotection of lamotrigine on hypoxic-ischemic brain damage in neonatal rats: Relations to administration time and doses

Lamotrigine (LTG), an antiepileptic drug, has been shown to be able to improve cerebral ischemic damage by limiting the presynaptic release of glutamate. The present study investigated further the neuroprotective effect of LTG on hypoxic-ischemic brain damage (HIBD) in neonatal rats and its relations to administration time and doses. The HIBD model was produced in 7-days old SD rats by left common carotid artery ligation followed by 2 h hypoxic exposure (8% oxygen). LTG was administered intraperitoneally with the doses of 5, 10, 20, and 40 mg/kg 3 h after operation and the dose of 20 mg/kg 1 h before and 3 h, 6 h after operation. Blood and brain were sampled 24 h after operation. Nissl staining, terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL), and neuron-specific enolase (NSE) immunohistochemical staining were used for morphological studies. Water content in left cortex and NSE concentration in serum were determined. LTG significantly reduced water content in the cerebral cortex, as well as the number of TUNEL staining neurons in the dentate gyrus and cortex in hypoxic-ischemia (HI) model. Furthermore, LTG significantly decreased the NSE level in serum and increased the number of NSE staining neurons in the cortex. These effects, except that on water content, were dose-dependent and were more remarkable in the pre-treated group than in the post-treated groups. These results demonstrate that LTG may have a neuroprotective effect on acute HIBD in neonates. The effect is more prominent when administrated with higher doses and before HI.

Longitudinal MRI and MRSI characterization of the quinolinic acid rat model for excitotoxicity: peculiar apparent diffusion coefficients and recovery of N-acetyl aspartate levels

Quinolinic acid (QA) induced striatal lesion is an important model for excitotoxicity that is also used for efficacy studies. To date, the morphological and spectroscopic indices of this model have not been studied longitudinally by MRI; therefore the objectives of this study were aimed at following the lesion progression and changes in N-acetyl aspartate (NAA) as viewed by MRI and MRSI, respectively, in-vivo over a period of 49 days. We found that the affected areas exhibited both high and low apparent diffusion coefficients (ADC) even 49 days post QA injection in three of the six tested animals. MRI-guided histological analysis correlated areas characterized by high ADCs on day 49 with cellular loss, while areas characterized by lower ADCs were correlated with macrophage infiltration (CD68 positive stain). Our MRSI study revealed an initial reduction of NAA levels in the lesioned striatum, which significantly recovered with time, although not to control levels. Total-striatum normalized NAA levels recovered from 0.67 +/- 0.15 (of the contralateral row) on day 1 to 0.90 +/- 0.12 on day 49. Our findings suggest that NAA should be considered as a marker for neuronal dysfunction, in addition to neuronal viability. Some behavioral indices could be correlated to permanent neuronal damage while others demonstrated a spontaneous recovery parallel to the NAA recovery. Our findings may have implications in efficacy-oriented studies performed on the QA model.

Altered open field behavior in rats induced by acute administration of 3-nitropropionic acid: possible glutamatergic and dopaminergic involvement

3-nitropropionic acid (3-NP), a substance used for modelling Huntington's disease, was given to male Wistar rats in a single 20 mg/kg b.w. dose, and the resulting behavioral alterations in spontaneous locomotor activity were measured after 30 minutes. To detect the involvement of neurotransmitter systems in this immediate effect, the NMDA antagonist MK-801 (0.8 mg/kg); as well as an agonist, quinpirole (QP, 5 mg/kg) and an antagonist, sulpiride (SP, 80 mg/kg) of the dopamine D2 receptors, were given before 3-NP to separate groups of rats. Controls were given saline. All substances were injected ip. 3-NP decreased the rats' locomotor, especially vertical, activity, whereas local activity was increased. Based on the further changes of 3-NP effects in the combination groups it could be concluded that dopaminergic rather than glutamatergic mechanisms were possibly involved in the acute behavioral effect of 3-NP.

Basal ganglia neuroprotection with anticonvulsants after energy stress: a comparative study

The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model provides a valuable paradigm of the energy deficiency disorders found in childhood. In such disorders, anticonvulsants may provide neuroprotection by modulating cellular energy consumption and by exerting favorable pleiotropic effects on neuronal survival. To verify such hypothesis, we tested the effects of levetiracetam, vigabatrin, gabapentine, pregabaline, tiagabine, clonazepam and lamotrigine on neuroprotection in the MPTP mouse model. The membrane dopamine transporter (DAT) density, which provides a reliable index of dopaminergic neurons survival in the basal ganglia, was assessed by semi-quantitative autoradiography of the striatum. Unlike all other anticonvulsants tested, lamotrigine provided a significant and dose-dependent neuroprotection in these experimental conditions. Lamotrigine, a widely used and well-tolerated molecule in children, could provide neuroprotection in various energy deficiency disorders.

Metabonomic characterization of the 3-nitropropionic acid rat model of Huntington's disease

3-Nitropropionic acid (3-NP)-induced neurotoxicity can be used as a model for the genetic neurodegenerative disorder Huntington's disease (HD). A metabolic profiling strategy was adopted to explore the biochemical consequences of 3-NP administered to rats in specific brain regions. (1)H NMR spectroscopy was used to characterize the metabolite composition of several brain regions following 3-NP-intoxication. Dose-dependent increases in succinate levels were observed in all neuroanatomical regions, resulting from the 3-NP-induced inhibition of succinate dehydrogenase. Global decreases in taurine and GABA were observed in the majority of brain regions, whereas altered lipid profiles were observed only in the globus pallidus and dorsal striatum. Depleted phosphatidylcholine and elevated glycerol levels, which are indicative of apoptosis, were also observed in the frontal cortex of the 3-NP model. Many of the metabolic anomalies are consistent with those reported in HD. The 3-NP-induced model of HD provides a means of monitoring potential mechanisms of pathology and therapeutic response for drug interventions, which can be efficiently assessed using metabolic profiling strategies.

LAMOTRIGINE REDUCES INTESTINAL I/R INJURY IN THE RAT

I/R injury of the intestine is a life-threatening emergency with mortality rates still more than 60%. We have investigated the protective effect of lamotrigine (LTG), an antiepileptic drug, which has an established neuroprotective effect, on intestinal I/R injury in rats. Forty-eight Wistar albino rats were divided into three groups: a sham-operated group (no I/R injury; n = 16), an ischemic control group (I/R, n = 16), and an LTG-treated group (pretreatment 5 mg kg-1 LTG + IR; n = 16). A marker for lipid peroxidation, malondialdehyde, free radical scavengers, glutathione peroxidase, catalase, and superoxide dismutase levels, an index of polymorphonuclear neutrophils, myeloperoxidase activity, and mucosal damage were investigated. Malondialdehyde levels, myeloperoxidase activity, and the severity of mucosal damage were decreased in the LTG group. Moreover, in the LTG group, glutathione peroxidase and superoxide dismutase levels were higher compared with the I/R group. The pretreatment of rats with LTG before intestinal ischemia ameliorates the mucosal damage in intestinal I/R injury probably by altering lipid peroxidation, neutrophil accumulation, and antioxidant activity.

Application of MRS to mouse models of neurodegenerative illness

The rapid development of transgenic mouse models of neurodegenerative diseases, in parallel with the rapidly expanding growth of MR techniques for assessing in vivo, non-invasive, neurochemistry, offers the potential to develop novel markers of disease progression and therapy. In this review we discuss the interpretation and utility of MRS for the study of these transgenic mouse and rodent models of neurodegenerative diseases such as Alzheimer's (AD), Huntington's (HD) and Parkinson's disease (PD). MRS studies can provide a wealth of information on various facets of in vivo neurochemistry, including neuronal health, gliosis, osmoregulation, energy metabolism, neuronal-glial cycling, and molecular synthesis rates. These data provide information on the etiology, natural history and therapy of these diseases. Mouse models enable longitudinal studies with useful time frames for evaluation of neuroprotection and therapeutic interventions using many of the potential MRS markers. In addition, the ability to manipulate the genome in these models allows better mechanistic understanding of the roles of the observable neurochemicals, such as N-acetylaspartate, in the brain. The argument is made that use of MRS, combined with correlative histology and other MRI techniques, will enable objective markers with which potential therapies can be followed in a quantitative fashion.

Memantine reduces striatal cell death with decreasing calpain level in 3-nitropropionic model of Huntington's disease

Huntington's disease has an increase in the activated calpain, which is enhanced by the NMDA receptor activation. We investigated the neuroprotective effect of memantine in 3-nitropropionic acid (3NP)-induced striatal degeneration model. Either memantine (20 mg/kg/day) or PBS was intraperitoneally administered for five days with 3NP continuous infusion. In the memantine-treated group, the striatal lesion volume, the number of TUNEL+ cells, and Fluoro-Jade C+ degenerating neurons were all decreased. Memantine increased Bcl-xl and decreased Bax level. Memantine also exerted an inhibitory effect on the micro-calpain level and decreased the huntingtin proteolytic fragments. Those rats treated with memantine showed less degree of weight loss at 5 days. Subsequently, memantine was found to have neuroprotective effects and save striatal cells with decreasing calpain levels in the 3NP model of Huntington's disease.

3-Nitropropionic acid: a mitochondrial toxin to uncover physiopathological mechanisms underlying striatal degeneration in Huntington's disease

Huntington's disease (HD) is a neurodegenerative disorder caused by a mutation in the gene encoding Huntingtin. The mechanisms underlying the preferential degeneration of the striatum, the most striking neuropathological change in HD, are unknown. Of those probably involved, mitochondrial defects might play an important role. The behavioural and anatomical similarities found between HD and models using the mitochondrial toxin 3-nitropropionic acid (3NP) in rats and primates support this hypothesis. Here, we discuss the recently identified mechanisms of 3NP-induced striatal degeneration. Two types of important factor have been identified. The first are the 'executioner' components that have direct roles in cell death, such as c-Jun N-terminal kinase and Ca2+-activated protease calpains. The second are 'environmental' factors, such as glutamate, dopamine and adenosine, which modulate the striatal degeneration induced by 3NP. Interestingly, these recent studies support the hypothesis that 3NP and mutated Huntingtin have certain mechanisms of toxicity in common, suggesting that the use of 3NP might give new insights into the pathogenesis of HD. Research on 3NP provides additional proof that the neurochemical environment of a given neurone can determine its preferential vulnerability in neurodegenerative diseases.

Antiepileptic drugs and neuroprotection: current status and future roles

There has been a growing interest in the use of antiepileptic drugs (AEDs) for neuroprotection, and in the possible role of AEDs in disease modification (i.e., antiepileptogenesis). Increased understanding of the mechanisms underlying brain injury has led to advances in the study of neuroprotection. However, defining the clinical paradigm and selecting appropriate outcomes to detect neuroprotective effects present challenges to clinicians studying the neuroprotective properties of drugs. Established AEDs, such as phenytoin, phenobarbital, and carbamazepine, have shown neuroprotective activity in an ischemic/hypoxic model of neuronal injury. Animal model studies also have suggested that newer AEDs, such as levetiracetam, topiramate, and zonisamide, may have neuroprotective or antiepileptogenic properties. However, the prevention of epileptogenesis by an AED has yet to be demonstrated in clinical trials. The future of neuroprotection may involve established and newer AEDs, as well as other compounds, such as immunophilins, caspase inhibitors, endocannabinoids, and antioxidants.

Excitatory amino acid neurotransmission

In recent years great progress has been made in understanding the function of ionotropic and metabotropic glutamate receptors; their pharmacology and potential therapeutic applications. It should be stressed that there are already N-methyl-D-aspartate (NMDA) antagonists in clinical use, such as memantine, which proves the feasibility of their therapeutic potential. It seems unlikely that competitive NMDA receptor antagonists and high-affinity channel blockers will find therapeutic use due to limiting side-effects, whereas agents acting at the glycineB site, NMDA receptor subtype-selective agents and moderate-affinity channel blockers are far more promising. This is supported by the fact that there are several glycineB antagonists, NMDA moderate-affinity channel blockers and NR2B-selective agents under development. Positive and negative modulators of AMPA receptors such as the AMPAkines and 2,3-benzodiazepines also show more promise than e.g. competitive antagonists. Great progress has also been made in the field of metabotropic glutamate receptors since the discovery of novel, allosteric modulatory sites for these receptors. Selective agents acting at these transmembrane sites have been developed that are more drug-like and have a much better access to the central nervous system than their competitive counterparts. The chapter will critically review preclinical and scarce clinical experience in the development of new ionotropic and metabotropic glutamate receptor modulators according to the following scheme: rational, preclinical findings in animal models and finally clinical experience, where available.

Mitochondrial inhibition and oxidative stress: reciprocating players in neurodegeneration

Although the etiology for many neurodegenerative diseases is unknown, the common findings of mitochondrial defects and oxidative damage posit these events as contributing factors. The temporal conundrum of whether mitochondrial defects lead to enhanced reactive oxygen species generation, or conversely, if oxidative stress is the underlying cause of the mitochondrial defects remains enigmatic. This review focuses on evidence to show that either event can lead to the evolution of the other with subsequent neuronal cell loss. Glutathione is a major antioxidant system used by cells and mitochondria for protection and is altered in a number of neurodegenerative and neuropathological conditions. This review also addresses the multiple roles for glutathione during mitochondrial inhibition or oxidative stress. Protein aggregation and inclusions are hallmarks of a number of neurodegenerative diseases. Recent evidence that links protein aggregation to oxidative stress and mitochondrial dysfunction will also be examined. Lastly, current therapies that target mitochondrial dysfunction or oxidative stress are discussed.

Lamotrigine suppresses neurophysiological responses to somatosensory stimulation in the rodent

Neurotransmitter release and voltage-gated ion channel activity in excitatory neurons are critical for understanding and interpreting neuroimaging signals. Couplings between changes in neural activity and energetic/vascular responses are assumed for interpretation of neuroimaging signals. To investigate involvement of neural events to neuroenergetic/neurovascular responses, we conducted multi-modal magnetic resonance imaging (MRI) measurements (at 7.0 T) and electrophysiological recordings (with high impedance microelectrodes) for local field potential (LFP) and spiking frequency (nu) in alpha-chloralose-anesthetized rats. The rats underwent forepaw stimulation before and after treatment of lamotrigine, a neuronal voltage-gated ion channel blocker and glutamate release inhibitor. Multi-modal MRI measurements of cerebral blood flow (CBF) and blood oxygenation level-dependent (BOLD) signal were combined to estimate changes in cerebral metabolic rate of oxygen consumption (CMRo2). Lamotrigine did not appreciably affect values of nu, CBF, and CMRo2 in the resting state. After lamotrigine treatment, evoked changes in LFP and nu were attenuated, which were consistent with commensurate declines in deltaCBF and deltaCMRo2. While number of evoked BOLD-activated voxels was considerably reduced with lamotrigine, intensities of voxels in middle cortical layers were affected to a lesser degree by lamotrigine. The results suggest that lamotrigine suppresses evoked neurophysiological (i.e., neural/energetic/vascular) responses, both in terms of volume of tissue activated and degree of activation in the foci. Since lamotrigine affects evoked responses but not the basal signals, it can be suggested that glutamate release and activity of voltage-gated ion channels are essential for initiating evoked energetic/vascular responses, and thereby important for interpretation of incremental changes in neuroimaging signal.

Protective effects of ginseng components in a rodent model of neurodegeneration

To test the proposed neuroprotective activity of whole ginseng extract and its components, we used 3-nitropropionic acid (3-NP), an inhibitor of succinate dehydrogenase, to produce neurodegeneration. Treatment with 3-nitropropionic acid (90 mg/kg) over a 5-day period resulted in severe impairment of movement and loss of neurons in the striatum. Pretreatment with a preparation from the whole root of American ginseng had no protective effects. Pretreatment with a preparation of ground leaves and stems, which contains greater levels of ginsenosides than ground root, improved the behavioral score and reduced the volume of the striatal lesion. A partial purification of American ginseng was performed to concentrate the putative protective components: Rb1, Rb3, and Rd (termed Rb extract). Pretreatment with the Rb extract significantly reduced the 3-nitropropionic acid-induced motor impairment and cell loss in the striatum, and it completely prevented any mortality. Significant effects on motor function, mortality, and the striatal lesion volume also were measured in animals pretreated with the individual ginsenosides, Rb1, Rb3, or Rd. The results demonstrate that some of the ginsenosides have neuroprotective activity, and that a partial purification of whole ginseng to concentrate the neuroprotective components may have utility as a neuroprotective agent.

Effect of nicotine on 3-nitropropionic acid-induced oxidative stress in synaptosomes

In this paper, the effect of nicotine on the oxidative changes produced by 3-nitropropionic acid (20 mg/kg i.p./day for 4 days) in striatal and cortical synaptosomes of Wistar rats was studied. The effects of 3-nitropropionic acid were evaluated as changes in the quantity of protein carbonyl groups, lipid peroxidation products, superoxide distumase activity and reduced succinate dehydrogenase activity. All changes were prevented by the pre-injection of nicotine (1.5 mg/kg i.p./day), beginning 4 days before and continuing for 4 days after the first injection of 3-nitropropionic acid. These findings indicate that: (i) 3-nitropropionic acid induces a state of oxidative stress in cortical and striatal synaptosomes and (ii) nicotine prevents oxidative stress induced by 3-nitropropinonic acid. In conclusion, the results show the ability of nicotine to modify neural response to 3-nitropropionic acid with the protective mechanism likely involving the antioxidative processes of nicotine.

Effect of lamotrigine treatment on epileptogenesis: an experimental study in rat

Prevention of epileptogenesis in patients with acute brain damaging insults like status epilepticus (SE) is a major challenge. We investigated whether lamotrigine (LTG) treatment started during SE is antiepileptogenic or disease-modifying. To mimic a clinical study design, LTG treatment (20 mg/kg) was started 2 h after the beginning of electrically induced SE in 14 rats and continued for 11 weeks (20 mg/kg per day for 2 weeks followed by 10 mg/kg per day for 9 weeks). One group of rats (n = 14) was treated with vehicle. Nine non-stimulated rats with vehicle treatment served as controls. Outcome measures were occurrence of epilepsy, severity of epilepsy, and histology (neuronal loss, mossy fiber sprouting). Clinical occurrence of seizures was assessed with 1-week continuous video-electroencephalography monitoring during the 11th (i.e. during treatment) and 14th week (i.e. after drug wash-out) after SE. LTG reduced the number of electrographic seizures during SE to 43% of that in the vehicle group (P < 0.05). In the vehicle group, 93% (13/14), and in the LTG group, 100% (14/14) of the animals, developed epilepsy. In both groups, 64% of the rats had severe epilepsy (seizure frequency >1 per day). The mean frequency of spontaneous seizures, seizure duration, or behavioral severity of seizures did not differ between groups. The severity of hippocampal neuronal damage and density of mossy fiber sprouting were similar. In LTG-treated rats with severe epilepsy, however, the duration of seizures was shorter (34 versus 54s, P < 0.05) and the behavioral seizure score was milder (1.4 versus 3.4, P < 0.05) during LTG treatment than after drug wash-out. LTG treatment started during SE and continued for 11 weeks was not antiepileptogenic but did not worsen the outcome. These data, together with earlier studies of other antiepileptic drugs, suggest that strategies other than Na(+)-channel blockade should be explored to modulate the molecular cascades leading to epileptogenesis after SE.

Magnetic resonance imaging and spectroscopy in assessing 3-nitropropionic acid-induced brain lesions: an animal model of Huntington’s disease

Huntington's disease (HD) is an inherited neurodegenerative disease, in which there is progressive motor and cognitive deterioration, and for which the pathogenesis of neuronal death remains controversial. Mitochondrial toxins like 3-nitropropionic acid (3-NP) and malonate, functioning as the inhibitors of the complex II of mitochondrial respiratory chain, have been found to effectively induce specific behavioral changes and selective striatal lesions in rats and non-human primates mimicking those in HD. Furthermore, several kinds of transgenic mouse models of HD have been recently developed, and used in the development and assessment of novel treatments for HD. In the past, most studies evaluating the animal models for HD were based on histological changes or in vitro neuronal cultures. With the emergence of advanced magnetic resonance technologies, non-invasive magnetic resonance imaging (MRI) and spectroscopy provide more detail of cerebral alterations, including the changes of cerebral structure, function and metabolites. These studies support the hypothesis that mitochondrial dysfunction with increased excitation of N-methyl-D-aspartate (NMDA) receptors can replicate the neurobehavioral changes, selective brain injury and neurochemical alterations in HD. The present review focuses on our work as well as that of others regarding 3-NP-induced neurotoxicity and other animal models of HD. Using both conventional and advanced MRI and spectroscopy, we summarize the pathogenesis and possible therapeutic strategies in chemical and transgenic models of HD. The results show magnetic resonance techniques to be powerful techniques in the evaluation of pathogenesis and therapeutic intervention for both chemical and transgenic models of HD.

Inflammatory neurodegeneration mediated by nitric oxide, glutamate, and mitochondria

In inflammatory, infectious, ischemic, and neurodegenerative pathologies of the central nervous system (CNS) glia become "activated" by inflammatory mediators, and express new proteins such as the inducible isoform of nitric oxide synthase (iNOS). Although these activated glia have benefi- cial roles, in vitro they potently kill cocultured neurons, and there is increasing evidence that they contribute to pathology in vivo. Nitric oxide (NO) from iNOS appears to be a key mediator of such glial-induced neuronal death. The high sensitivity of neurons to NO is partly due to NO causing inhibition of respiration, rapid glutamate release from both astrocytes and neurons, and subsequent excitotoxic death of the neurons. NO is a potent inhibitor of mitochondrial respiration, due to reversible binding of NO to cytochrome oxidase in competition with oxygen, resulting in inhibition of energy production and sensitization to hypoxia. Activated astrocytes or microglia cause a potent inhibition of respiration in cocultured neurons due to glial NO inhibiting cytochrome oxidase within the neurons, resulting in ATP depletion and glutamate release. In some conditions, glutamate- induced neuronal death can itself be mediated by N-methyl-D-aspartate (NMDA)-receptor activation of the neuronal isoform of NO synthase (nNOS) causing mitochondrial damage. In addition NO can be converted to a number of reactive derivatives such as peroxynitrite, NO2, N2O3, and S-nitrosothiols that can kill cells in part by inhibiting mitochondrial respiration or activation of mitochondrial permeability transition, triggering neuronal apoptosis or necrosis.

Acute and chronic alterations in calcium homeostasis in 3-nitropropionic acid-treated human NT2-N neurons

3-Nitropropionic acid (3-NP), an irreversible inhibitor of succinate dehydrogenase, induced ATP depletion and both necrosis and apoptosis in human NT2-N neurons. Necrosis occurred predominantly within the first two days, and increased in a dose-dependent fashion with the concentration of 3-NP, whereas apoptosis was observed after 24 h or later at a similar rate in 0.1 mM and 5 mM 3-NP. We focused our efforts on intracellular calcium homeostasis during the first 48 h in 1 mM 3-NP, a period during which 10% of the neurons died by necrosis and 3% by apoptosis. All NT2-N neurons showed a stereotyped [Ca(2+)](i) rise, from 48+/-2 to 140+/-12 nM (mean +/-S.E.M.), during the first 2 h in 3-NP. Despite severe ATP depletion, however, [Ca(2+)](i) remained above 100 nM in only 17% and 25% of the NT2-N neurons after 24 and 48 h in 3-NP, respectively, indicating that most neurons were able to recover from acute [Ca(2+)](i) rise, and suggesting that chronic [Ca(2+)](i) dysregulation is a better indicator of subsequent necrosis. Blockade of N-methyl-D-aspartate-glutamate receptor by MK-801 substantially ameliorated 3-NP-induced ATP depletion, subsequent chronic [Ca(2+)](i) elevation, and survival. Moreover, xestospongin C, an inhibitor of endoplasmic reticulum Ca(2+) release, enhanced the capacity of NT2-N neurons to maintain [Ca(2+)](i) homeostasis and resist necrosis while subjected to sustained energy deprivation. As far as we know, this report is the first to employ human neurons to study the pathophysiology of 3-NP neurotoxicity.

The mechanisms of neuronal death produced by mitochondrial toxin 3-nitropropionic acid: the roles of N-methyl-D-aspartate glutamate receptors and mitochondrial calcium overload

Previous studies showed that 3-nitropropionic acid, an irreversible inhibitor of succinate dehydrogenase, produced neuronal death secondary to perturbed intracellular calcium homeostasis. However, the response of intramitochondrial calcium ([Ca(2+)](m)) to 3-nitropropionic acid remains unknown. In this study, we investigated the roles of and relationships among [Ca(2+)](m) overload, mitochondrial reactive oxygen species, and mitochondrial membrane depolarization in 3-nitropropionic acid-induced neuronal death. Following 1 mM 3-nitropropionic acid treatment on primary rat neuronal cultures, there was a gradual increase of [Ca(2+)](m) beginning at 2-4 h post 3-nitropropionic acid application, and a twofold increase of mitochondrial reactive oxygen species at 4 h. These were followed by mitochondrial membrane depolarization at 6-8 h post-treatment. By inhibiting [Ca(2+)](m) uptake, Ruthenium Red attenuated the production of reactive oxygen species, and prevented the 3-nitropropionic acid-induced mitochondrial membrane depolarization and 70% of apoptotic neuronal death (P<0.001). Inhibition of caspase activation attenuated the elevation of [Ca(2+)](m) (P<0.001), indicating that caspase activation plays a role in the elevation of [Ca(2+)](m). MK-801, an antagonist of N-methyl-D-aspartate (NMDA) glutamate receptors, prevented 3-nitropropionic acid-induced [Ca(2+)](m) elevation, caspase-3 activation, mitochondrial depolarization, and neuronal death. We conclude that the activation of NMDA glutamate receptor contributes to mitochondrial alterations induced by 3-nitropropionic acid. Inhibition of its activation and [Ca(2+)](m) overload with subsequent mitochondrial membrane depolarization can therefore attenuate the neuronal death induced by 3-nitropropionic acid.

Progress report on new antiepileptic drugs: a summary of the Sixth Eilat Conference (EILAT VI)

The Sixth Eilat Conference on New Antiepileptic Drugs (AEDs) took place in Taormina, Sicily, Italy from 7th to 11th April, 2002. Basic scientists, clinical pharmacologists and neurologists from 27 countries attended the conference, whose main themes included dose-response relationships with conventional and recent AEDs, teratogenic effects of conventional and recent AEDs, update on clinical implications of AED metabolism, prevention of epileptogesis, and seizure aggravation by AEDs. According to tradition, the central part of the conference was devoted to a review of AEDs in development, as well to updates on AEDs, which have been marketed in recent years. This article summarizes the information presented on drugs in preclinical and clinical development, including carabersat (SB-204269), CGX-1007 (Conantokin-G), pregabalin, retigabine (D-23129), safinamide, SPD421 (DP-VPA), SPM 927, talampanel and valrocemide (TV 1901). Updates on fosphenytoin, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, vigabatrin, zonisamide, new formulations of valproic acid, and the antiepileptic vagal stimulator device are also presented.

Involvement of superoxide in excitotoxicity and DNA fragmentation in striatal vulnerability in mice after treatment with the mitochondrial toxin, 3-nitropropionic acid

Oxidative stress and excitotoxicity have been implicated in selective striatal vulnerability caused by the mitochondrial toxin, 3-nitropropionic acid (3-NP), which may simulate Huntington's disease in animals and humans. The detailed mechanism of the role of superoxide in striatal vulnerability induced by 3-NP is still unknown. The authors investigated oxidative cellular injury and DNA fragmentation after systemic 3-NP injection in wild-type (Wt) mice and mutant mice with a deficiency in manganese superoxide dismutase (MnSOD; Sod2 -/+). Furthermore, they investigated the effects of decortication after 3-NP treatment in Sod2 -/+ mice, and copper/zinc SOD (CuZnSOD) treatment in recently developed Sod2 -/+ mice that overexpress CuZnSOD (SOD1 +/- / Sod2 -/+ mice). Oxidized hydroethidine, 8-hydroxyguanosine immunoreactivity, and nitrotyrosine immunoreactivity were increased in the Sod2 -/+ mice compared with the Wt mice after 3-NP treatment (P < 0.001). Decortication completely abolished oxidative striatal damage after 3-NP treatment in the Sod2 -/+ mice. Increased CuZnSOD attenuated DNA fragmentation and striatal lesion volume after 3-NP treatment in the Sod2 -/+ mice (P < 0.001). These data suggest that production of superoxide may be a critical step to excitotoxicity and subsequent DNA fragmentation in selective striatal vulnerability after 3-NP treatment.

Neuroprotective potential of ionotropic glutamate receptor antagonists

From the therapeutic point of view, the real challenge is not only to improve the symptoms, but to interfere with the pathomechanism of the disease. That is why a considerable interest has recently been devoted to developing glutamate receptor antagonists (mainly of the NMDA type) for acute and chronic neurodegeneration. Developing such a treatment that slows down the progression of the disease is extremely time and cost consuming. At present there is consensus that competitive NMDA receptor antagonists will not find therapeutic applications, in contrast to agents acting at the glycine(B) site, or channel blockers. Recently, at least seven glycine(B) antagonists (e.g. ACEA 1021, GV-150526, GV-196771A, ZD-9379, MRZ 2/576) and over 10 NMDA channel blockers (e.g. Remacemide, ARL-15896AR, HU-211, ADCI, CNS-5161, Neramexane-MRZ 2/579) have been under development, most of them as neuroprotective agents for acute (stroke, trauma) or chronic insult (e.g. Huntington's or Alzheimer's disease). Several substances selective for NR2B NMDA receptor subtypes such as eliprodil, CP-101606 and Ro-25-6981 have been claimed to have a good neuroprotective profile. This presentation is an attempt to critically review preclinical and scarce clinical experience in the development of new NMDA receptor antagonists as neuroprotective agents according to the following scheme: rational, preclinical findings in animal models and finally clinical experience if available. The general impression is that NMDA receptor antagonists may find use in chronic type of neurodegeneration while AMPA antagonists seem to show better promise in acute insult.

The promise of new antiepileptic drugs

Epilepsy is the most common serious disorder of the brain and comprises a wide range of different conditions with varying aetiologies. The long-established antiepileptic drugs (AEDs) control seizures in 50% of patients developing partial seizures, and 60-70% of those developing generalized seizures. Several AEDs were made available in the 1990s. These drugs have efficacy, but have had only a modest impact on those with refractory epilepsies. A 50% seizure reduction, which is commonly used as an endpoint in clinical trials, confers little benefit to a patient. Of the newer AEDs, lamotrigine and oxcarbazepine are now licensed for use as monotherapy and vigabatrin has a monotherapy licence for infantile spasms. Careful and prolonged postmarketing surveillance is essential to detect adverse effects, which may not be evident in premarketing clinical trials. At this time, there are 10 AEDs currently in varying stages of clinical development. Current strategies for selecting an AED for a particular patient are crude. Magnetic resonance spectroscopic measures of cerebral neuro-transmitters and genetic analysis may allow better prediction of which drug is most likely to be efficacious and to have low risk of adverse effects. Present AEDs suppress the occurrence of seizures. Agents that prevent the development of epilepsy and which protect the brain from the consequences of seizures would be of great value, but it will be difficult to prove their effectiveness. At present AEDs are given continually and systemically. Local drug delivery is feasible and could avoid the adverse effects of AEDs. The combination of local drug delivery with prediction of seizure occurrence could revolutionize the treatment of currently refractory epilepsies.

Lamotrigine plus leukocyte filtration as a neuroprotective strategy in experimental hypothermic circulatory arrest

BACKGROUND

Lamotrigine and leukocyte filtration seem to improve cerebral protection during experimental hypothermic circulatory arrest (HCA). This study was performed to evaluate whether their combined use may further improve cerebral protection.

METHODS

Twenty-four pigs undergoing 75-minute period of HCA at 20 degrees C were randomly assigned to receive saline; lamotrigine (20 mg/kg) before HCA (L); or lamotrigine (20 mg/kg) before HCA plus leukocyte filtration before and after HCA (L + LF).

RESULTS

Seven animals (87%) in the L + LF group, 4 (50%) in the L group, and 3 (37%) in the control group were alive on the seventh postoperative day. The median electroencephalogram burst recovery was 94% in the L + LF group (p = 0.024 versus control group), 81% in the L group, and 64% in the control group. Among the surviving animals, the median behavioral scores were 9, 9, and 6 at the seventh day, respectively (p = 0.005 between the L + LF group and the control group). The median histopathologic score was 14 in the L + LF group (p = 0.046 versus control group), 14.5 in the L group (p = 0.062 versus control group), and 21 in the control group.

CONCLUSIONS

Lamotrigine has neuroprotective effect during HCA. The combined use of lamotrigine and LF may further improve the survival outcome.

A bile acid protects against motor and cognitive deficits and reduces striatal degeneration in the 3-nitropropionic acid model of Huntington's disease

There is currently no effective treatment for Huntington's disease (HD), a progressive, fatal, neurodegenerative disorder characterized by motor and cognitive deterioration. It is well established that HD is associated with perturbation of mitochondrial energy metabolism. Tauroursodeoxycholic acid (TUDCA), a naturally occurring bile acid, can stabilize the mitochondrial membrane, inhibit the mitochondrial permeability transition, decrease free radical formation, and derail apoptotic pathways. Here we report that TUDCA significantly reduced 3-nitropropionic acid (3-NP)-mediated striatal neuronal cell death in cell culture. In addition, rats treated with TUDCA exhibited an 80% reduction in apoptosis and in lesion volumes associated with 3-NP administration. Moreover, rats which received a combination of TUDCA + 3-NP exhibited sensorimotor and cognitive task performance that was indistinguishable from that of controls, and this effect persisted at least 6 months. Bile acids have traditionally been used as therapeutic agents for certain liver diseases. This is the first demonstration, however, that a bile acid can be delivered to the brain and function as a neuroprotectant and thus may offer potential therapeutic benefit in the treatment of certain neurodegenerative diseases.

Effect of lamotrigine treatment on status epilepticus-induced neuronal damage and memory impairment in rat

Status epilepticus causes neuronal damage that is associated with cognitive impairment. The present study examined whether a novel antiepileptic drug, lamotrigine (LTG), alleviates status epilepticus-induced temporal lobe damage and memory impairment, and compared its efficacy with carbamazepine. Status epilepticus was induced by electric stimulation of the perforant pathway (PP) in rats. Treatment with LTG (12.5 mg/kg, twice a day) was started either 3 days before (preLTG group) or 1 h after (postLTG group) a 60 min PP stimulation. Treatment with carbamazepine (CBZ; 30 mg/kg, twice a day) was started 3 days before (CBZ group) a 60 min PP stimulation. All treatments were continued for 2 weeks. Thereafter, the severity of seizures, seizure-induced neuronal damage, quantitative electroencephalogram (EEG), and memory impairment were compared between vehicle-treated unstimulated and stimulated controls, LTG-treated rats, and CBZ-pretreated rats. Both in the preLTG and postLTG groups, damage to hilar somatostatin-immunoreactive neurons, hippocampal CA3b and CA3a pyramidal cells, and the piriform cortex was mild and did not differ from that in unstimulated controls. Furthermore, CA3c damage in the preLTG group did not differ from that in unstimulated controls. Vehicle-treated stimulated controls and CBZ-pretreated rats, however, had significant damage in the hilus, CA3 subregions, and piriform cortex compared with unstimulated controls (P<0.05 for the stimulated side, contralateral side, or both). Treatment with LTG or CBZ had no effect on the number or duration of behavioral seizures during PP stimulation. They did not affect the baseline EEG or status epilepticus-induced slowing of the EEG. Also, the status epilepticus-induced spatial memory impairment in the Morris water-maze was not attenuated by treatment with LTG or CBZ. Our data demonstrate that treatment with LTG has a mild neuroprotective effect on status epilepticus-induced neuronal damage in rats even when administered after the beginning of status epilepticus.

N-Acetylaspartate, a marker of both cellular dysfunction and neuronal loss: its relevance to studies of acute brain injury

To evaluate the contribution of cellular dysfunction and neuronal loss to brain N-acetylaspartate (NAA) depletion, NAA was measured in brain tissue by HPLC and UV detection in rats subjected to cerebral injury, associated or not with cell death. When lesion was induced by intracarotid injection of microspheres, the fall in NAA was related to the degree of embolization and to the severity of brain oedema. When striatal lesion was induced by local injection of malonate, the larger the lesion volume, the higher the NAA depletion. However, reduction of brain oedema and striatal lesion by treatment with the lipophilic iron chelator dipyridyl (20 mg/kg, 1 h before and every 8 h after embolization) and the inducible nitric oxide synthase inhibitor aminoguanidine (100 mg/kg given 1 h before malonate and then every 9 h), respectively, failed to ameliorate the fall in NAA. Moreover, after systemic administration of 3-nitropropionic acid, a marked reversible fall in NAA striatal content was observed despite the lack of tissue necrosis. Overall results show that cellular dysfunction can cause higher reductions in NAA level than neuronal loss, thus making of NAA quantification a potential tool for visualizing the penumbra area in stroke patients.

Expression of brain-derived neurotrophic factor in cortical neurons is regulated by striatal target area

Changes in BDNF expression after different types of brain insults are related to neuroprotection, stimulation of sprouting, and synaptic reorganization. In the cerebral cortex, an autocrine-paracrine mechanism for BDNF has been proposed because the distribution patterns of BDNF and TrkB expression are almost identical. Moreover, cortical BDNF is anterogradely transported to the striatum, suggesting a role of BDNF in the functional interaction between the two brain regions. Here we have examined the expression of this neurotrophin in the cerebral cortex after various striatal lesions. Intrastriatal injection of quinolinate, kainate, 3-nitropropionic acid, or colchicine increased BDNF mRNA levels in cerebral cortex. In contrast, stimulation of neuronal activity in the striatum did not change cortical BDNF expression. Both excitatory amino acids increased BDNF expression in neurons of cortical layers II/III, V, and VI that project to the striatum. Moreover, grafting a BDNF-secreting cell line prevented both the loss of striatal neurons and the cortical upregulation of BDNF induced by excitotoxins. Because retrograde transport in the corticostriatal pathway was intact after striatal lesions, our results suggest that striatal damage upregulates endogenous BDNF in corticostriatal neurons by a transneuronal mechanism, which may constitute a protective mechanism for striatal and/or cortical cells.

Orphenadrine prevents 3-nitropropionic acid-induced neurotoxicity in vitro and in vivo

1. Previous studies indicate that 3-nitropropionic acid (3-NPA) neurotoxicity involves the excitotoxic activation of N-methyl-D-aspartate (NMDA) receptors. Thus, we examined the effect of orphenadrine (an anticholinergic drug with NMDA receptor antagonist properties) on 3-NPA neurotoxicity in both cultured rat cerebellar granule cells (CGCs) and in rats. 2. Orphenadrine protected CGCs from 3-NPA-induced mortality, as assessed by both the neutral red viability assay and laser scanning cytometry, using propidium iodide staining. 3. For rats, two indirect markers of neuronal damage were used: the binding of [(3)H]-PK 11195 to the peripheral-type benzodiazepine receptor (PBR), a microglial marker, and expression of the 27 kD heat-shock protein (HSP27), a marker of activated astroglia. Systemic administration of 3-NPA (30 mg kg(-1) per day for 3 days) induced a 170% increase in [(3)H]-PK 11195 binding, and expression of HSP27. 4. Both the increase in [(3)H]-PK 11195 and HSP 27 expression were prevented by previous administration of 30 mg kg(-1) per day of orphenadrine for 3 days. Lower doses (10 and 20 mg kg(-1)) had no protective effect. Orphenadrine also reduced 3-NPA-induced mortality in a dose-dependent manner. 5. We propose that orphenadrine or orphenadrine-like drugs could be used to treat neurodegenerative disorders mediated by overactivation of NMDA receptors.

Neuroprotective and neurorestorative strategies for neuronal injury

Mechanisms of neuronal cell death in apoptosis and necrosis are examined. Neurotoxic processes underlying cellular destruction may involve N-methyl-D-aspartate (NMDA) receptor activation and/or activation of neuronal nitric oxide synthase but the depletion of energy and generation of free radicals appears to be critical. In Alzheimer's disease the damaging effects of peroxynitrite and exposure to beta-amyloid peptide is evident. Mitochondrial dysfunction is involved in several neurodegenerative diseases including Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease as well as Alzheimer's disease and in these disorders the innovations offered by techniques ranging from transgenic mouse models of the disorder to cell culture preparations are remarkable. Agents of neuroprotection and neurorestoration possess either characteristics specific to particular disorders or have a general applicability or both. The vast array of agents available are for the most part the objectives of laboratory examinations but an increasing selection of compounds are reaching the clinical necessities thereby influencing current strategic notions to modify tactical contingencies. Among the agents listed are included: inhibitors of the enzyme poly-ADP-ribose polymerase, inhibition of apoptotic cell death, agents acting on mitochondrial permeability transition, excitatory amino acid antagonists, applications of neurotrophins, immunophilins, agents influencing heme oxygenase-1 expression and iron sequestration in aging astroglia, improvements in mitochondrial energy production or buffering, and finally dopaminemimetics with differential affinities for dopamine receptors.