Riluzole Treatment Research Articles

Riluzole effects on behavioral sensitivity and the development of axonal damage and spinal modifications that occur after painful nerve root compression

Cervical radiculopathy is often attributed to cervical nerve root injury, which induces extensive degeneration and reduced axonal flow in primary afferents. Riluzole inhibits neuro-excitotoxicity in animal models of neural injury. The authors undertook this study to evaluate the antinociceptive and neuroprotective properties of riluzole in a rat model of painful nerve root compression. A single dose of riluzole (3 mg/kg) was administered intraperitoneally at Day 1 after a painful nerve root injury. Mechanical allodynia and thermal hyperalgesia were evaluated for 7 days after injury. At Day 7, the spinal cord at the C-7 level and the adjacent nerve roots were harvested from a subgroup of rats for immunohistochemical evaluation. Nerve roots were labeled for NF200, CGRP, and IB4 to assess the morphology of myelinated, peptidergic, and nonpeptidergic axons, respectively. Spinal cord sections were labeled for the neuropeptide CGRP and the glutamate transporter GLT-1 to evaluate their expression in the dorsal horn. In a separate group of rats, electrophysiological recordings were made in the dorsal horn. Evoked action potentials were identified by recording extracellular potentials while applying mechanical stimuli to the forepaw. Even though riluzole was administered after the onset of behavioral sensitivity at Day 1, its administration resulted in immediate resolution of mechanical allodynia and thermal hyperalgesia (p < 0.045), and these effects were maintained for the study duration. At Day 7, axons labeled for NF200, CGRP, and IB4 in the compressed roots of animals that received riluzole treatment exhibited fewer axonal swellings than those from untreated animals. Riluzole also mitigated changes in the spinal distribution of CGRP and GLT-1 expression that is induced by a painful root compression, returning the spinal expression of both to sham levels. Riluzole also reduced neuronal excitability in the dorsal horn that normally develops by Day 7. The frequency of neuronal firing significantly increased (p < 0.045) after painful root compression, but riluzole treatment maintained neuronal firing at sham levels. These findings suggest that early administration of riluzole is sufficient to mitigate nerve root-mediated pain by preventing development of neuronal dysfunction in the nerve root and the spinal cord.

The Effects of Minocycline or Riluzole Treatment on Spinal Root Avulsion–Induced Pain in Adult Rats

Spinal root avulsion produces tactile and thermal hypersensitivity, neurodegeneration, and microglial and astrocyte activation in both the deafferented and the adjacent intact spinal cord segments. Following avulsion of the fifth lumbar spinal root, immediate and prolonged treatment with riluzole or minocycline for 2 weeks altered the development of behavioral hypersensitivity. Riluzole delayed the onset of thermal and tactile hypersensitivity and partially reversed established pain behavior. Minocycline effectively prevented and reversed both types of behavioral change. Histologic analysis revealed that both drugs reduced microglial staining in the spinal cord, with minocycline being more effective than riluzole. Astrocyte activation was ameliorated to a lesser extent. Surprisingly, neither drug provided a neuroprotective effect on avulsed motoneurons. PerspectiveImmediate treatment of spinal root avulsion injuries with minocycline or riluzole prevents the onset of evoked pain hypersensitivity by reducing microglial cell activation. When treatment is delayed, minocycline, but not riluzole, reverses pre-established hypersensitivity. Thus, these drugs may provide a new translational treatment option for chronic avulsion injury pain.

Exploring Cross-Talk Between Oxidative Damage and Excitotoxicity and the Effects of Riluzole in the Rat Cortex After Exposure to Methylmercury

Methylmercury (MeHg) is a ubiquitous environmental toxin that causes neurologic and developmental diseases. Oxidative damage and excitotoxicity are putative mechanisms, which underlie MeHg-induced neurotoxicity. In this study, the cross-talk between the oxidative damage and excitotoxicity pathways and the protective effects of riluzole in the rat cortex were explored. Rats were injected with MeHg and/or riluzole, and cold vapor atomic fluorescence spectrometry, hematoxylin and eosin staining, flow cytometry, fluorescence assays, spectrophotometry, real-time PCR, and Western blotting were used to evaluate neurotoxicity. The present study showed that (1) MeHg accumulated in the cerebral cortex and caused pathology. (2) MeHg caused oxidative damage by inducing glutathione (GSH) depletion, reactive oxygen species (ROS) production, inhibition of antioxidant enzyme activity, and alteration of the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. (3) MeHg disrupted the glutamate transporters (GluTs), glutamate-glutamine cycle, and N-methyl-D-aspartate receptor expression and induced excitotoxicity. (4) Excitotoxicity resulted in disruption of GSH synthesis, calcium overloading, oxidative damage, and excessive ROS production. (5) Pretreatment with riluzole antagonized MeHg neurotoxicity by down regulating cross-talk between the oxidative damage and excitotoxicity pathways. In conclusion, the cross-talk between the oxidative damage and excitotoxicity pathways caused by MeHg exposure was linked by GluTs and calcium and inhibited by riluzole treatment.

Partial block by riluzole of muscle sodium channels in myotubes from amyotrophic lateral sclerosis patients.

Denervated muscles undergo fibrillations due to spontaneous activation of voltage-gated sodium (Na+) channels generating action potentials. Fibrillations also occur in patients with amyotrophic lateral sclerosis (ALS). Riluzole, the only approved drug for ALS treatment, blocks voltage-gated Na+ channels, but its effects on muscle Na+ channels and fibrillations are yet poorly characterized. Using patch-clamp technique, we studied riluzole effect on Na+ channels in cultured myotubes from ALS patients. Needle electromyography was used to study fibrillation potentials (Fibs) in ALS patients during riluzole treatment and after one week of suspension. Patients were clinically characterized in all recording sessions. In myotubes, riluzole (1 μM, a therapeutic concentration) reduced Na+ current by 20%. The rate of rise and amplitude of spikes evoked by depolarizing stimuli were also reduced. Fibs were detected in all patients tested during riluzole treatment and riluzole washout had no univocal effect. Our study indicates that, in human myotubes, riluzole partially blocks Na+ currents and affects action potentials but does not prevent firing. In line with this in vitro finding, muscle Fibs in ALS patients appear to be largely unaffected by riluzole.

The Neuroprotection Exerted by Memantine, Minocycline and Lithium, against Neurotoxicity of CSF from Patients with Amyotrophic Lateral Sclerosis, Is Antagonized by Riluzole

In a recent study we found that cerebrospinal fluids (CSFs) from amyotrophic lateral sclerosis (ALS) patients caused 20-30% loss of cell viability in primary cultures of rat embryo motor cortex neurons. We also found that the antioxidant resveratrol protected against such damaging effects and that, surprisingly, riluzole antagonized its protecting effects. Here we have extended this study to the interactions of riluzole with 3 other recognized neuroprotective agents, namely memantine, minocycline and lithium. We found: (1) by itself riluzole exerted neurotoxic effects at concentrations of 3-30 µ<smlcap>M</smlcap>; this cell damage was similar to that elicited by 30 µ<smlcap>M</smlcap> glutamate and a 10% dilution of ALS/CSF; (2) memantine (0.1-30 µ<smlcap>M</smlcap>), minocycline (0.03-1 µ<smlcap>M</smlcap>) and lithium (1-80 µg/ml) afforded 10-30% protection against ALS/CSF-elicited neurotoxicity, and (3) at 1-10 µ<smlcap>M</smlcap>, riluzole antagonized the protection afforded by the 3 agents. These results strongly support the view that at the riluzole concentrations reached in the brain of patients, the neurotoxic effects of this drug could be masking the potential neuroprotective actions of new compounds being tested in clinical trials. Therefore, in the light of the present results, the inclusion of a group of patients free of riluzole treatment may be mandatory in future clinical trials performed in ALS patients with novel neuroprotective compounds.

Abstract 3889: GRM1 over-expression in melanoma cells promotes microvesicle formation which functions in stimulating angiogenesis.

Abstract Our group has reported that metabotropic glutamate receptor 1 (GRM1) as an oncogene and a potential therapeutic target for melanoma. More than 60% of human melanoma expresses GRM1, while normal melanocytes do not. In a Phase-0 trial of riluzole (an oral inhibitor of GRM1) in patients with advanced melanoma we showed suppression of the PI3K/AKT and MAPK pathways in melanoma specimens in 34% of the patients. Our group found that enhanced expression of GRM1 in a subclone of a melanoma cell line (UACC903) that normally expresses low levels of GRM1 stimulated angiogenesis via activation of the AKT-mTOR-HIF1-IL8, VEGF signaling pathway. Increasing GRM1 expression promoted membrane blebbing (a phenomenon that appears to lead to microvesicle formation) and riluzole treatment inhibited this effect. Suppression of GRM1 expression using an inducible siRNA construct inhibits the blebbing phenomena and microvesicle formation. Therefore, we hypothesize that GRM1 expression promotes microvesicle formation that may be involved in stimulating angiogenesis and tumor progression. Through electron-microscope and flow cytometry analysis, we have confirmed that increased GRM1 expression enhanced microvesicle secretion into the medium in cell culture and that knocking down GRM1 expression significantly reduced the quantity of microvesicle secretion. Furthermore, intra-tumor injection of collected microvesicles into two different melanoma xenograft tumors (UACC903 and C8161) demonstrated that the microvesicles formed from high GRM1 expressing cells promoted tumor growth and angiogenesis. We also showed that microvesicles from high GRM1 expressing cells increased endothelial cell proliferation exhibited measured using a BrdU incorporation assay. Our preliminary data demonstrate that GRM1 expression promotes microvesicle formation and that these microvesicles are associated with angiogenesis. Research on the molecular events associated with the phenomenon is ongoing. Citation Format: Jasmine J. Koo, Yu Wen, Jiadong Li, Suzie Chen, James Goydos. GRM1 over-expression in melanoma cells promotes microvesicle formation which functions in stimulating angiogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3889. doi:10.1158/1538-7445.AM2013-3889

The Neuroprotective Drug Riluzole Acts via Small Conductance Ca2+-Activated K+Channels to Ameliorate Defects in Spinal Muscular Atrophy Models

Spinal muscular atrophy (SMA), a recessive neuromuscular disorder, is caused by diminished function of the Survival Motor Neuron (SMN) protein. To define the cellular processes pertinent to SMA, parallel genetic screens were undertaken in Drosophila and Caenorhabditis elegans SMA models to identify modifiers of the SMN loss of function phenotypes. One class of such genetic modifiers was the small conductance, Ca(2+)-activated K(+) (SK) channels. SK channels allow efflux of potassium ions when intracellular calcium increases and can be activated by the neuroprotective drug riluzole. The latter is the only drug with proven, albeit modest, efficacy in the treatment of amyotrophic lateral sclerosis. It is unclear if riluzole can extend life span or ameliorate symptoms in SMA patients as previous studies were limited and of insufficient power to draw any conclusions. The critical biochemical target of riluzole in motor neuron disease is not known, but the pharmacological targets of riluzole include SK channels. We examine here the impact of riluzole in two different SMA models. In vertebrate neurons, riluzole treatment restored axon outgrowth caused by diminished SMN. Additionally, riluzole ameliorated the neuromuscular defects in a C. elegans SMA model and SK channel function was required for this beneficial effect. We propose that riluzole improves motor neuron function by acting on SK channels and suggest that SK channels may be important therapeutic targets for SMA patients.

Delayed Post-Injury Administration of Riluzole Is Neuroprotective in a Preclinical Rodent Model of Cervical Spinal Cord Injury

Riluzole, a sodium/glutamate antagonist has shown promise as a neuroprotective agent. It is licensed for amyotrophic lateral sclerosis and is in clinical trial development for spinal cord injury (SCI). This study investigated the therapeutic time-window and pharmacokinetics of riluzole in a rodent model of cervical SCI. Rats were treated with riluzole (8 mg/kg) at 1 hour (P1) and 3 hours (P3) after injury or with vehicle. Afterward, P1 and P3 groups received riluzole (6 (mg/kg) every 12 hours for 7 days. Both P1 and P3 animals had significant improvements in locomotor recovery as measured by open field locomotion (BBB score, BBB subscore). Von Frey stimuli did not reveal an increase in at level or below level mechanical allodynia. Sensory-evoked potential recordings and quantification of axonal cytoskeleton demonstrated a riluzole-mediated improvement in axonal integrity and function. Histopathological and retrograde tracing studies demonstrated that delayed administration leads to tissue preservation and reduces apoptosis and inflammation. High performance liquid chromatography (HPLC) was undertaken to examine the pharmacokinetics of riluzole. Riluzole penetrates the spinal cord in 15 min, and SCI slowed elimination of riluzole from the spinal cord, resulting in a longer half-life and higher drug concentration in spinal cord and plasma. Initiation of riluzole treatment 1 and 3 hours post-SCI led to functional, histological, and molecular benefits. While extrapolation of post-injury time windows from rat to man is challenging, evidence from SCI-related biomarker studies would suggest that the post-injury time window is likely to be at least 12 hours in man.

The impact of clinical factors, riluzole and therapeutic interventions on ALS survival: A population based study in Modena, Italy

The prognostic role of riluzole, enteral nutrition (EN), non-invasive ventilation (NIV) and interdisciplinary care in ALS is still debated. A population based study has been performed focusing on ALS survival, with particular attention to prognostic factors and therapeutic intervention. All patients diagnosed with ALS between 2000 and 2009 and residing in Modena, Italy, have been registered. A centre for motor neuron disease (MND) has been active in our province since 2000, in addition to a prospective registry collecting all incident cases. One hundred and ninety-three incident cases have been collected during the 10 years of the study. Results demonstrated that median survival was 41 months (the overall three-year and five-year survival rates being 54.36% and 28.81%, respectively). Based on univariate analysis, factors related to survival were: age at diagnosis, gender, site of onset, phenotype, riluzole treatment and tracheostomy. In the Cox multivariable model, the factors independently related to a longer survival were age (p < 0.01), site of onset (p = 0.02) and riluzole treatment (p < 0.01), with a median gain in survival of 29 months (patients aged < 55 years compared with patients ≥ 55 years), 20 months (spinal versus bulbar onset), and 12 months (riluzole, yes vs. no), respectively. In conclusion, the study has confirmed the prognostic role of clinical features, but has surprisingly demonstrated that riluzole prolonged life significantly longer than NIV and EN. This observational study described the effects of ALS management in a setting that may approximate routine clinical practice more closely than randomized controlled trial (RCT); effects of uncontrolled potential confounders, however, cannot be excluded.

Open Randomized Clinical Trial on JWSJZ Decoction for the Treatment of ALS Patients

Objective. To investigate the efficacy and safety of the traditional Chinese medicine Jiawei Sijunzi (JWSJZ) decoction for the treatment of patients with amyotrophic lateral sclerosis (ALS). Methods. Forty-eight patients with ALS were divided into a JWSJZ group (n = 24) and a control group (n = 24) using a randomized number method. Together with the basic treatment for ALS, JWSJZ decoction was added to the treatment regimen of patients in the JWSJZ group or Riluzole was administered to the control group for 6 months. Neurologists evaluated the treated and control patients using the ALS functional rating scale (ALSFRS) before, 3 and 6 months after starting the additional treatments. Results. The ALSFRS scores in both groups were lower 3 and 6 months after treatment than before. There was a significant difference at 6 months after treatment between the subgroups of patients with ALS whose limbs were the initial site of attack. No serious adverse effects were observed in the JWSJZ group. Conclusion. JWSJZ decoction may be a safe treatment for ALS, and may have delayed the development of ALS, especially in the subgroup of patients in whom the limbs were attacked first when compared with Riluzole treatment.

Riluzole and Prognostic Factors in Amyotrophic Lateral Sclerosis Long-term and Short-term Survival: A Population-Based Study of 1149 Cases in Taiwan

BackgroundAmyotrophic lateral sclerosis (ALS) is a rare disease in Taiwan; thus, estimation of ALS mortality is difficult. We evaluated factors associated with ALS survival in Taiwan.MethodsThe study enrolled 1149 Taiwanese with a primary diagnosis of ALS during 1999–2008. Follow-up information was available for all patients; mean (SD) duration of follow-up was 2.91 (2.62) years. Medical interventions, including noninvasive positive pressure ventilation (NIPPV), tracheotomy, gastrostomy, and riluzole, were included in time-dependent survival analysis.ResultsOf the 1149 ALS patients, 438 (38.12%) died during follow-up. Mortality in the first year was 16%, which was 13 times (95% CI 11.1–15.2) the age- and sex-standardized rate of the general population in Taiwan. The average annual crude mortality rate was 13.1% (person-years). Factors significantly associated with increased mortality were male sex, advanced age, rural residence, lower economic status, no tracheotomy, and no riluzole treatment. Significant predictors of long-term versus average survival were younger age at diagnosis, being a dependent or receiving social welfare, and NIPPV support. Significant predictors of short-term versus average survival were older age, being employed, no tracheotomy, and no riluzole use.ConclusionsThe results support the use of riluzole to improve ALS survival. Patients who received riluzole and underwent tracheotomy had the best survival.

PERCUTANEOUS ENDOSCOPIC GASTROSTOMY (PEG) IN MND: A 10-YEAR EXPERIENCE

Enteral feeding is offered to many patients diagnosed with Motor Neuron Disease (MND) experiencing dysphagia and impaired nutritional status. The evidence for survival advantage after PEG insertion is weakly positive...

Riluzole effect on occipital cortex: A structural and spectroscopy pilot study

BackgroundTo investigate the mechanism underlying the anxiolytic properties of riluzole, a glutamate-modulating agent, we previously studied the effect of this drug on hippocampal N-acetylaspartate (NAA) and volume in patients with generalized anxiety disorder (GAD). In the same cohort, we now extend our investigation to the occipital cortex, a brain region that was recently implicated in the antidepressant effect of riluzole. MethodsFourteen medication-free adult patients with GAD received 8-week of open-label riluzole. Ten healthy subjects served as a comparison group. The healthy group did not receive riluzole treatment. Both groups underwent magnetic resonance imaging and spectroscopy at baseline and at the end of Week 8. Hamilton Anxiety Rating Scale (HAM-A) and Penn State Worry Questionnaire (PSWQ) were used as the primary and secondary outcome measures, respectively. ResultsAt baseline, we found clusters of increased cortical thickness in the occipital region in GAD compared to healthy subjects. In the right hemisphere, 8 weeks of treatment reduced occipital cortical thickness in the GAD group (t=3.67, p=0.004). In addition, the improvement in HAM-A scores was negatively correlated with post-treatment right occipital NAA (r=−0.68, p=0.008), and with changes in NAA levels (r=−0.53, p=0.051). In the left hemisphere, we found positive associations between changes in occipital cortical thickness and improvement in HAM-A (r=0.60, p=0.04) and PSWQ (r=0.62, p=0.03). ConclusionThese pilot findings implicate the occipital cortex as a brain region associated with pathology and clinical improvement in GAD. In addition, the region specific effect of riluzole implies a distinct pathophysiology in the occipital cortex – compared to other, previously studied, frontolimbic brain structures.

Riluzole blocks human muscle acetylcholine receptors

Riluzole, the only drug available against amyotrophic lateral sclerosis (ALS), has recently been shown to block muscle ACh receptors (AChRs), raising concerns about possible negative side-effects on neuromuscular transmission in treated patients. In this work we studied riluzole's impact on the function of muscle AChRs in vitro and on neuromuscular transmission in ALS patients, using electrophysiological techniques. Human recombinant AChRs composed of α(1)β(1)δ subunits plus the γ or ε subunit (γ- or ε-AChR) were expressed in HEK cells or Xenopus oocytes. In both preparations, riluzole at 0.5 μm, a clinically relevant concentration, reversibly reduced the amplitude and accelerated the decay of ACh-evoked current if applied before coapplication with ACh. The action on γ-AChRs was more potent and faster than on ε-AChRs. In HEK outside-out patches, riluzole-induced block of macroscopic ACh-evoked current gradually developed during the initial milliseconds of ACh presence. Single channel recordings in HEK cells and in human myotubes from ALS patients showed that riluzole prolongs channel closed time, but has no effect on channel conductance and open duration. Finally, compound muscle action potentials (CMAPs) evoked by nerve stimulation in ALS patients remained unaltered after a 1 week suspension of riluzole treatment. These data indicate that riluzole, while apparently safe with regard to synaptic transmission, may affect the function of AChRs expressed in denervated muscle fibres of ALS patients, with biological consequences that remain to be investigated.

Drug treatment for spinal muscular atrophy type I

Spinal muscular atrophy (SMA) is caused by degeneration of anterior horn cells of the spinal cord, which leads to progressive muscle weakness. Children with SMA type I will never be able to sit without support and usually die by the age of two years. There are no known efficacious drug treatments that influence the course of the disease. This is an update of a review first published in 2009. To evaluate whether drug treatment is able to slow or arrest the disease progression of SMA type I, and to assess if such therapy can be given safely. Drug treatment for SMA types II and III is the topic of a separate updated Cochrane review. We searched the Cochrane Neuromuscular Disease Group Specialized Register (8 March 2011), CENTRAL (The Cochrane Library 2011, Issue 1), MEDLINE (January 1991 to February 2011), EMBASE (January 1991 to February 2011) and ISI Web of Knowledge (January 1991 to 8 March 2011). We searched the Clinical Trials Registry of the U.S. National Institute of Health (www.ClinicalTrials.gov) (8 March 2011) to identify additional trials that had not yet been published. We sought all randomised or quasi-randomised trials that examined the efficacy of drug treatment for SMA type I. Participants had to fulfil the clinical criteria and have a deletion or mutation of the SMN1 gene (5q11.2-13.2) confirmed by genetic analysis.The primary outcome measure was time from birth until death or full time ventilation. Secondary outcome measures were development of rolling, sitting or standing within one year after the onset of treatment, and adverse events attributable to treatment during the trial period. Two authors (RW and AV) independently reviewed and extracted data from all potentially relevant trials. For included studies, pooled relative risks and standardised mean differences were to be calculated to assess treatment efficacy. One small randomised controlled study comparing riluzole treatment to placebo for 10 SMA type 1 children was identified and included in the original review. No further trials were identified for the update in 2011. Regarding the primary outcome measure, three of seven children treated with riluzole were still alive at the ages of 30, 48 and 64 months, whereas all three children in the placebo group died; but the difference was not statistically significant. Regarding the secondary outcome measures, none of the children in the riluzole or placebo group developed the ability to roll, sit or stand, and no adverse effects were observed. For several reasons the overall quality of the study was low, mainly because the study was too small to detect an effect and because of baseline differences. Follow-up of the 10 included children was complete. No drug treatment for SMA type I has been proven to have significant efficacy.

Riluzole Treatment Reduces Motoneuron Death Induced by Axotomy in Newborn Rats

Nerve injury in neonatal rats leads to considerable motoneuron death. We investigated whether treatment with riluzole (a presynaptic inhibitor of glutamate release) is able to enhance survival of motor units (MUs) in the slow soleus (Sol) and fast extensor digitorum longus (EDL) muscles after sciatic nerve crush in newborn rats. Examination of 3- to 4-month-old rats revealed a beneficial effect of riluzole treatment after injury carried out on the first day after birth. At this time increased MU survival occurred in both the Sol and EDL muscles. In rats with nerve injury carried out on the second day after birth, increased MU survival occurred only in the Sol. We conclude that although riluzole treatment can rescue motoneurons destined to die and improve muscle performance, its beneficial effect is age-dependent, and the difference between the rescue of Sol and EDL MUs may be due to the slower maturation of motoneurons to soleus muscle. These findings have important implications regarding the motoneuron properties required for riluzole's beneficial effect.

Course of Improvement in Depressive Symptoms to a Single Intravenous Infusion of Ketamine vs Add-on Riluzole: Results from a 4-Week, Double-Blind, Placebo-Controlled Study

The N-methyl-D-aspartate antagonist ketamine has rapid antidepressant effects in patients with treatment-resistant major depression (TRD); these effects have been reported to last for 1 week in some patients. However, the extent and duration of this antidepressant effect over longer periods has not been well characterized under controlled conditions. Riluzole, a glutamatergic modulator with antidepressant and synaptic plasticity-enhancing effects, could conceivably be used to promote the antidepressant effects of ketamine. This study sought to determine the extent and time course of antidepressant improvement to a single-ketamine infusion over 4 weeks, comparing the addition of riluzole vs placebo after the infusion. Forty-two subjects (18-65) with TRD and a Montgomery-Asberg Depression Rating Scale (MADRS) score of ≥ 22 received a single intravenous infusion of ketamine (0.5 mg/kg). Four to six hours post-infusion, subjects were randomized to double-blind treatment with either riluzole (100-200 mg/day; n=21) or placebo (n=21) for 4 weeks. Depressive symptoms were rated daily. A significant improvement (P<0.001) in MADRS scores from baseline was found. The effect size of improvement with ketamine was initially large and remained moderate throughout the 28-day trial. Overall, 27% of ketamine responders had not relapsed by 4 weeks following a single ketamine infusion. The average time to relapse was 13.2 days (SE=2.2). However, the difference between the riluzole and placebo treatment groups was not significant, suggesting that the combination of riluzole with ketamine treatment did not significantly alter the course of antidepressant response to ketamine alone.

O-50 - A glutamate-modulating drug, riluzole, is one of the candidate drugs for new generation antidepressants and/or anxiolytics

Growing evidence indicated that the glutamatergic neurotransmitter system is central to the neurobiology and treatment of mood and anxiety disorders. Riluzole, a drug currently used to slow the progression of amyotrophic lateral sclerosis, is one of the candidate drugs that modulate glutamatergic neurotransmission in the central nervous system. Recently, several open-label clinical trials have suggested that riluzole reduces symptoms of treatment-resistant major depression, obsessive-compulsive disorder and generalized anxiety disorder. Previously, we reported that riluzole rapidly attenuates the hyperemotional responses found in the olfactory bulbectomized rats. This animal model exhibits hyperemotional behavior that may mimic anxiety, aggression and irritability found in depressed patients, suggesting the possible use of riluzole in combating the symptoms of anxiety and depression. Interestingly, we first found that a single riluzole treatment had rapid anti-hyperemotional effects in the rats. In addition, we demonstrated that single riluzole treatment significantly decreased extracellular glutamate levels in medial prefrontal cortex of the rats by in vivo microdialysis examination. Our results propose a hypothesis that riluzole rapidly improve symptoms in depressed patients, as a non-monoamine-based antidepressant. In conclusion, our results suggest that a glutamate-modulating drug, riluzole, is one of the candidate drugs for new generation antidepressants and/or anxiolytics.

Effect of prolonged riluzole exposure on cultured motoneurons in a mouse model of ALS.

Riluzole is the only FDA-approved drug to treat amyotrophic lateral sclerosis, but its long-term effects on motoneurons are unknown. Therefore, we treated primary mouse spinal cord cultures with 2 μM riluzole for 4-9 days and then used whole cell patch clamp to record the passive and active properties of both wild-type and SOD1(G93A) motoneurons. At this concentration, riluzole blocks >50% of the sodium component of a persistent inward current that plays a major role in determining motoneuron excitability. Prolonged riluzole treatment significantly decreased the amplitude of the persistent inward current. This effect was specific for SOD1(G93A) motoneurons, where the amplitude decreased by 55.4%. In addition, prolonged treatment hyperpolarized the resting membrane potential as well as the voltage onset and voltage maximum of the persistent inward current (∼2-3 mV in each case). These effects appeared to offset one another and resulted in no change in the firing properties. In a subset of cells, acute reapplication of 2 μM riluzole during the recording decreased repetitive firing and the persistent inward current, which is consistent with the normal effects of riluzole. The downregulation of the persistent inward current in response to prolonged riluzole administration is in contrast to the strong upregulation of this same current after descending neuromodulatory drive to the cord is lost following spinal injury. This dichotomy suggests that decreased activation of G protein-coupled pathways can induce upregulation in the persistent inward current but that direct channel block is ineffective.

Serum &lt;emph type="ital"&gt;N&lt;/emph&gt; -acetylaspartate Level in Amyotrophic Lateral Sclerosis

N -acetylaspartate (NAA) level is a biomarker of functional integrity and vitality in neurons. In vivo multisection proton ((1)H)-magnetic resonance spectroscopy studies indicate that NAA level decreases in specific cortical brain areas of patients with amyotrophic lateral sclerosis (ALS). To study NAA level in serum samples as a possible biomarker of ALS. Serum NAA assay by liquid chromatography-mass spectrometry in a case-control series. Department of Neurological and Psychiatric Sciences, Policlinico, University of Bari, Bari, Italy. One hundred twelve consecutive patients with ALS and 51 age- and sex-matched healthy control subjects. General estimating equations tested associations between serum NAA level and clinical variables in patients with ALS. Serum NAA level was significantly higher in ALS cases than in controls. Multivariate logistic regression analysis showed a direct association between serum NAA level and the presence of ALS. After stratifying serum NAA level based on the median value (0.171 mmol/L), the age- and sex-adjusted odds ratio for ALS was 19.97 (95% confidence interval, 7.18-55.55) (P < .001). N -acetylaspartate level did not differ across ALS clinical phenotypes. Riluzole treatment did not affect NAA level. A significant correlation was found between serum NAA level and ALS progression rate. High serum NAA level was found in patients with ALS, which may relate to greater excretion of NAA into the blood circulation following increased release of this metabolite from damaged neurons. The correlation between serum NAA level and disease progression rate suggests that it may be a useful biomarker of ALS.