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Kassa J, Zdarova Karasova J. Combination of acetylcholinesterase inhibitors and NMDA receptor antagonists increases survival rate in soman-poisoned mice. Toxicol Mech Methods 2023; 33:590-595. [PMID: 37051629 DOI: 10.1080/15376516.2023.2202730] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 01/19/2023] [Accepted: 04/08/2023] [Indexed: 04/14/2023]
Abstract
Organophosphorus nerve agents pose a global threat to both military personnel and civilian population, because of their high acute toxicity and insufficient medical countermeasures. Commonly used drugs could ameliorate the intoxication and overall medical outcomes. In this study, we tested the drugs able to alleviate the symptoms of Alzheimer's disease (donepezil, huperzine A, memantine) or Parkinson's disease (procyclidine). They were administered to mice before soman intoxication in terms of their: i) protection potential against soman toxicity and ii) influence on post-exposure therapy consisting of atropine and asoxime (also known as oxime HI-6). Their pretreatment effect was not significant, when administered alone, but in combination (acetylcholinesterase inhibitor such as denepezil or huperzine A with NMDA antagonist such as memantine or procyclidine) they lowered the soman toxicity more than twice. These combinations also positively influenced the efficacy of post-exposure treatment in a similar fashion; the combinations increased the therapeutic effectiveness of antidotal treatment. In conclusion, the most effective combination - huperzine A and procyclidine - lowered the toxicity three times and improved the post-exposure therapy efficacy more than six times. These results are unprecedented in the published literature.
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Affiliation(s)
- Jiri Kassa
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
| | - Jana Zdarova Karasova
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Hradec Kralove, Czech Republic
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Niquet J, Nguyen D, de Araujo Furtado M, Lumley L. Treatment of cholinergic-induced status epilepticus with polytherapy targeting GABA and glutamate receptors. Epilepsia Open 2023; 8 Suppl 1:S117-S140. [PMID: 36807554 PMCID: PMC10173853 DOI: 10.1002/epi4.12713] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 02/15/2023] [Indexed: 02/23/2023] Open
Abstract
Despite new antiseizure medications, the development of cholinergic-induced refractory status epilepticus (RSE) continues to be a therapeutic challenge as pharmacoresistance to benzodiazepines and other antiseizure medications quickly develops. Studies conducted by Epilepsia. 2005;46:142 demonstrated that the initiation and maintenance of cholinergic-induced RSE are associated with trafficking and inactivation of gamma-aminobutyric acid A receptors (GABAA R) thought to contribute to the development of benzodiazepine pharmacoresistance. In addition, Dr. Wasterlain's laboratory reported that increased N-methyl-d-aspartate receptors (NMDAR) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPAR) contribute to enhanced glutamatergic excitation (Neurobiol Dis. 2013;54:225; Epilepsia. 2013;54:78). Thus, Dr. Wasterlain postulated that targeting both maladaptive responses of reduced inhibition and increased excitation that is associated with cholinergic-induced RSE should improve therapeutic outcome. We currently review studies in several animal models of cholinergic-induced RSE that demonstrate that benzodiazepine monotherapy has reduced efficacy when treatment is delayed and that polytherapy with drugs that include a benzodiazepine (eg midazolam and diazepam) to counter loss of inhibition, concurrent with an NMDA antagonist (eg ketamine) to reduce excitation provide improved efficacy. Improved efficacy with polytherapy against cholinergic-induced seizure is demonstrated by reduction in (1) seizure severity, (2) epileptogenesis, and (3) neurodegeneration compared with monotherapy. Animal models reviewed include pilocarpine-induced seizure in rats, organophosphorus nerve agent (OPNA)-induced seizure in rats, and OPNA-induced seizure in two mouse models: (1) carboxylesterase knockout (Es1-/- ) mice which, similarly to humans, lack plasma carboxylesterase and (2) human acetylcholinesterase knock-in carboxylesterase knockout (KIKO) mice. We also review studies showing that supplementing midazolam and ketamine with a third antiseizure medication (valproate or phenobarbital) that targets a nonbenzodiazepine site rapidly terminates RSE and provides further protection against cholinergic-induced SE. Finally, we review studies on the benefits of simultaneous compared with sequential drug treatments and the clinical implications that lead us to predict improved efficacy of early combination drug therapies. The data generated from seminal rodent studies of efficacious treatment of cholinergic-induced RSE conducted under Dr. Wasterlain's guidance suggest that future clinical trials should treat the inadequate inhibition and temper the excess excitation that characterize RSE and that early combination therapies may provide improved outcome over benzodiazepine monotherapy.
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Affiliation(s)
- Jerome Niquet
- Department of NeurologyDavid Geffen School of Medicine at UCLALos AngelesCaliforniaUSA
- Epilepsy Research LaboratoryVeterans Affairs Greater Los Angeles Healthcare SystemLos AngelesCaliforniaUSA
| | - Donna Nguyen
- Neuroscience DepartmentU.S. Army Medical Research Institute of Chemical Defense (USAMRICD)Aberdeen Proving GroundMarylandUSA
| | | | - Lucille Lumley
- Neuroscience DepartmentU.S. Army Medical Research Institute of Chemical Defense (USAMRICD)Aberdeen Proving GroundMarylandUSA
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Kassa J, Karasova JZ. Memantine and Its Combination with Acetylcholinesterase Inhibitors in Pharmacological Pretreatment of Soman Poisoning in Mice. Neurotox Res 2021; 39:1487-1494. [PMID: 34292503 DOI: 10.1007/s12640-021-00394-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 06/18/2021] [Accepted: 07/07/2021] [Indexed: 10/20/2022]
Abstract
Nerve agents pose a real threat to both the military and civil populations, but the current treatment of the poisoning is unsatisfactory. Thus, we studied the efficacy of prophylactic use of memantine alone or in combination with clinically used reversible acetylcholinesterase inhibitors (pyridostigmine, donepezil, rivastigmine) against soman. In addition, we tested their influence on post-exposure therapy consisting of atropine and asoxime. Pyridostigmine alone failed to decrease the acute toxicity of soman. But all clinically used acetylcholinesterase inhibitors administered alone reduced the acute toxicity, with donepezil showing the best efficacy. The combination of memantine with reversible acetylcholinesterase inhibitors attenuated soman acute toxicity significantly. The pretreatment administered alone or in combinations influenced the efficacy of post-exposure treatment in a similar fashion: (i) pyridostigmine or memantine alone did not affect the antidotal treatment, (ii) centrally acting reversible acetylcholinesterase inhibitors alone increased the antidotal treatment slightly, (iii) combination of memantine with reversible acetylcholinesterase inhibitors increased the antidotal treatment more markedly. In conclusion, memantine alone failed to decrease the acute toxicity of soman or increase post-exposure antidotal treatment efficacy. The combination of memantine with donepezil significantly increased post-exposure effectiveness (together 5.12, pretreatment alone 1.72). Both drugs, when applied together, mitigate soman toxicity and boost post-exposure treatment.
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Affiliation(s)
- Jiri Kassa
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Králové, Czech Republic
| | - Jana Zdarova Karasova
- Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence, Trebesska 1575, 500 01, Hradec Králové, Czech Republic.
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Stojiljković MP, Škrbić R, Jokanović M, Kilibarda V, Bokonjić DR, Maksimović M. Effects of memantine and its metabolite Mrz 2/373 on soman-induced inhibition of acetylcholinesterase in vitro. Chem Biol Interact 2021; 342:109463. [PMID: 33831382 DOI: 10.1016/j.cbi.2021.109463] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 11/30/2020] [Accepted: 03/29/2021] [Indexed: 01/01/2023]
Abstract
Memantine is the non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist, used in the treatment of Alzheimer's disease. It is also known that memantine pretreatment assured protection of skeletal muscles from poisoning with nerve agents and an interaction between memantine and AChE was proposed. In the study presented we examined interactions of memantine and its main metabolite (1-amino-3-hydroxymethyl-5-methyl adamantine, Mrz 2/373) with AChE in vitro as well as their effect on kinetics of the soman-induced AChE inhibition and aging. The results have shown that memantine and Mrz 2/373 exerted concentration-dependent inhibition of AChE, with Mrz 2/373 being a more potent inhibitor than the parent compound. Addition of soman 7.5 nmol/l induced gradual AChE inhibition that became almost complete after 20 min. Memantine (0.1, 0.5 and 1 mmol/l) and Mrz 2/373 (0.1, 0.5 and 1 mmol/l) concentration-dependently slowed down the AChE inhibition. After 30 min of incubation of AChE with soman, 5 min of aging and 20 min of reactivation by asoxime (HI-6 dichloride), AChE activity was 8.1% in control medium, 30.7% and 41.9% after addition of 1 and 10 mmol/l memantine, and 16.1% after addition of 1 mmol/l Mrz 2/373. It was concluded that it is possible that memantine and Mrz 2/373 can prevent AChE from inhibition by soman, which could, along with known memantine's neuroprotective activity, explain its potent antidotal effect in soman poisoning. The potential effect on aging of the soman-AChE complex warrants further studies.
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Affiliation(s)
- Miloš P Stojiljković
- Department of Pharmacology, Toxicology and Clinical Pharmacology, Faculty of Medicine, University of Banja Luka, the Republic of Srpska, Bosnia and Herzegovina; National Poison Control Centre, Military Medical Academy, University of Defence, Belgrade, Serbia.
| | - Ranko Škrbić
- Department of Pharmacology, Toxicology and Clinical Pharmacology, Faculty of Medicine, University of Banja Luka, the Republic of Srpska, Bosnia and Herzegovina
| | | | - Vesna Kilibarda
- National Poison Control Centre, Military Medical Academy, University of Defence, Belgrade, Serbia
| | - Dubravko R Bokonjić
- National Poison Control Centre, Military Medical Academy, University of Defence, Belgrade, Serbia
| | - Matej Maksimović
- National Poison Control Centre, Military Medical Academy, University of Defence, Belgrade, Serbia
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Spampanato J, Bealer SL, Smolik M, Dudek FE. Delayed Adjunctive Treatment of Organophosphate-Induced Status Epilepticus in Rats with Phenobarbital, Memantine, or Dexmedetomidine. J Pharmacol Exp Ther 2020; 375:59-68. [PMID: 32873622 DOI: 10.1124/jpet.120.000175] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 07/16/2020] [Indexed: 12/15/2022] Open
Abstract
Organophosphate (OP) exposure induces status epilepticus (SE), a medical emergency with high morbidity and mortality. Current standard medical countermeasures lose efficacy with time so that treatment delays, in the range of tens of minutes, result in increasingly poor outcomes. As part of the Countermeasures Against Chemical Threats Neurotherapeutics Screening Program, we previously developed a realistic model of delayed treatment of OP-induced SE using the OP diisopropyl fluorophosphate (DFP) to screen compounds for efficacy in the termination of SE and elimination of neuronal death. Male rats were implanted for electroencephalogram (EEG) recordings 7 days prior to experimentation. Rats were then exposed to DFP, and SE was induced for 60 minutes and then treated with midazolam (MDZ) plus one of three antiseizure drugs (ASDs)-phenobarbital (PHB), memantine (MEM), or dexmedetomidine (DMT)-in conjunction with antidotes. EEG was recorded for 24 hours, and brains were stained with Fluoro-Jade B for quantification of degenerating neurons. We found that PHB + MDZ induced a prolonged suppression of SE and reduced neuronal death. MEM + MDZ treatment exacerbated SE and increased mortality; however, surviving rats had fewer degenerating neurons. DMT + MDZ significantly suppressed SE with only a minimal reduction in neuronal death. These data demonstrate that delayed treatment of OP-induced SE with other ASDs, when added to MDZ, can achieve greater seizure suppression with additional reduction in degenerating neurons throughout the brain compared with MDZ alone. The effect of a drug on the severity of seizure activity did not necessarily determine the drug's effect on neuronal death under these conditions. SIGNIFICANCE STATEMENT: This study assesses the relative effectiveness of three different delayed-treatment regimens for the control of organophosphate-induced status epilepticus and reduction of subsequent neuronal death. The data demonstrate the potential for highly effective therapies despite significant treatment delay and a potential disconnect between seizure severity and neuronal death.
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Affiliation(s)
- Jay Spampanato
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, Utah
| | - Steven L Bealer
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, Utah
| | - Melissa Smolik
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, Utah
| | - F Edward Dudek
- Department of Neurosurgery, University of Utah School of Medicine, Salt Lake City, Utah
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Prophylactic potential of memantine against soman poisoning in rats. Toxicology 2019; 416:62-74. [DOI: 10.1016/j.tox.2019.01.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 01/15/2019] [Accepted: 01/18/2019] [Indexed: 11/19/2022]
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Jackson C, Ardinger C, Winter KM, McDonough JH, McCarren HS. Validating a model of benzodiazepine refractory nerve agent-induced status epilepticus by evaluating the anticonvulsant and neuroprotective effects of scopolamine, memantine, and phenobarbital. J Pharmacol Toxicol Methods 2019; 97:1-12. [PMID: 30790623 PMCID: PMC6529248 DOI: 10.1016/j.vascn.2019.02.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/05/2019] [Accepted: 02/14/2019] [Indexed: 12/26/2022]
Abstract
INTRODUCTION Organophosphorus nerve agents (OPNAs) irreversibly block acetylcholinesterase activity, resulting in accumulation of excess acetylcholine at neural synapses, which can lead to a state of prolonged seizures known as status epilepticus (SE). Benzodiazepines, the current standard of care for SE, become less effective as latency to treatment increases. In a mass civilian OPNA exposure, concurrent trauma and limited resources would likely cause a delay in first response time. To address this issue, we have developed a rat model to test novel anticonvulsant/ neuroprotectant adjuncts at delayed time points. METHODS For model development, adult male rats with cortical electroencephalographic (EEG) electrodes were exposed to soman and administered saline along with atropine, 2-PAM, and midazolam 5, 20, or 40 min after SE onset. We validated our model using three drugs: scopolamine, memantine, and phenobarbital. Using the same procedure outlined above, rats were given atropine, 2-PAM, midazolam and test treatment 20 min after SE onset. RESULTS Using gamma power, delta power, and spike rate to quantify EEG activity, we found that scopolamine was effective, memantine was minimally effective, and phenobarbital had a delayed effect on terminating SE. Fluoro-Jade B staining was used to assess neuroprotection in five brain regions. Each treatment provided significant protection compared to saline + midazolam in at least two brain regions. DISCUSSION Because our data agree with previously published studies on the efficacy of these compounds, we conclude that this model is a valid way to test novel anticonvulsants/ neuroprotectants for controlling benzodiazepine-resistant OPNA-induced SE and subsequent neuropathology.
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Affiliation(s)
| | | | | | | | - Hilary S. McCarren
- Corresponding author at: U.S. Army Medical Research Institute of Chemical Defense, 8350 Ricketts Point Road, Aberdeen Proving Ground, MD 21010, USA
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Leeman-Markowski BA, Meador KJ, Moo LR, Cole AJ, Hoch DB, Garcia E, Schachter SC. Does memantine improve memory in subjects with focal-onset epilepsy and memory dysfunction? A randomized, double-blind, placebo-controlled trial. Epilepsy Behav 2018; 88:315-324. [PMID: 30449328 PMCID: PMC7261142 DOI: 10.1016/j.yebeh.2018.06.047] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 06/02/2018] [Accepted: 06/25/2018] [Indexed: 10/28/2022]
Abstract
OBJECTIVE Excitotoxic injury involving N-methyl-d-aspartate (NMDA) receptor hyperactivity contributes to epilepsy-related memory dysfunction (ERMD). Current treatment strategies for ERMD have limited efficacy and fail to target the underlying pathophysiology. The present pilot study evaluated the efficacy of memantine, an NMDA receptor antagonist, for the treatment of ERMD in adults with focal-onset seizures. METHODS Subjects underwent cognitive testing at baseline, after a 13-week randomized, parallel-group, double-blinded phase (of memantine titrated to 10 mg bid or placebo), and following a 13-week open-label extension phase (of memantine titrated to 10 mg bid). The selective reminding test (SRT) continuous long-term retrieval (CLTR) score and 7/24 Spatial Recall Test learning score served as the primary outcome measures. Secondary measures included tests of attention span, fluency, visual construction, and response inhibition, as well as assessments of quality of life, depression, sleepiness, and side effects. RESULTS Seventeen subjects contributed data to the blinded phase (n = 8 memantine, n = 9 placebo). No significant differences were seen between groups on the primary or secondary outcome measures. Pooled data at the end of the open-label phase from 10 subjects (initially randomized to memantine n = 3 or placebo n = 7) demonstrated statistically significant improvement from baseline in CLTR score, memory-related quality of life, spatial span, and response inhibition. No significant changes were evident in depression, sleepiness, side effects, or seizure frequency throughout the trial. SIGNIFICANCE Results demonstrated no significant effect of memantine on cognition when assessed at the end of the blinded period. Pooled data at the end of the open-label phase showed significant improvement over baseline performance in measures of verbal memory, frontal-executive function, and memory-related quality of life. These improvements, however, may be due to practice effects and should be interpreted cautiously. Findings suggest a favorable safety profile of memantine in the setting of epilepsy.
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Affiliation(s)
- Beth A. Leeman-Markowski
- Research Service, VA New York Harbor Healthcare System, New York, NY, USA,Department of Neurology, New York University Langone Medical Center, New York, NY, USA,Corresponding author at: 423 E. 23rd St., New York, NY 10010, USA. (B.A. Leeman-Markowski)
| | - Kimford J. Meador
- Department of Neurology & Neurological Sciences, Stanford University School of Medicine, Palo Alto, CA, USA
| | - Lauren R. Moo
- Geriatric Research Education and Clinical Center, Edith Nourse Rogers Memorial Veterans Hospital, Bedford, MA, USA,Department of Neurology, Massachusetts General Hospital, Boston, MA, USA,Harvard Medical School, Boston, MA, USA
| | - Andrew J. Cole
- Department of Neurology, Massachusetts General Hospital, Boston, MA, USA,Harvard Medical School, Boston, MA, USA
| | - Daniel B. Hoch
- Department of Neurology, Massachusetts General Hospital, Boston, MA, USA,Harvard Medical School, Boston, MA, USA
| | - Eduardo Garcia
- Tufts University School of Medicine, Boston, MA, USA,Newton–Wellesley Neurology Associates, PC, Newton Lower Falls, MA, USA
| | - Steven C. Schachter
- Harvard Medical School, Boston, MA, USA,Beth Israel Deaconess Medical Center, Boston, MA, USA
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RETRACTED ARTICLE: Cromakalim, a Potassium Channel Opener, Ameliorates Organophosphate- and Carbamate-Induced Seizures in Mice. ARCHIVES OF NEUROSCIENCE 2017. [DOI: 10.5812/archneurosci.64773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Zebrafish is a predictive model for identifying compounds that protect against brain toxicity in severe acute organophosphorus intoxication. Arch Toxicol 2016; 91:1891-1901. [PMID: 27655295 PMCID: PMC5364264 DOI: 10.1007/s00204-016-1851-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 09/15/2016] [Indexed: 12/13/2022]
Abstract
Acute organophosphorus (OP) intoxication is a worldwide clinical and public health problem. In addition to cholinergic crisis, neurodegeneration and brain damage are hallmarks of the severe form of this toxidrome. Recently, we generated a chemical model of severe acute OP intoxication in zebrafish that is characterized by altered head morphology and brain degeneration. The pathophysiological pathways resulting in brain toxicity in this model are similar to those described in humans. The aim of this study was to assess the predictive power of this zebrafish model by testing the effect of a panel of drugs that provide protection in mammalian models. The selected drugs included “standard therapy” drugs (atropine and pralidoxime), reversible acetylcholinesterase inhibitors (huperzine A, galantamine, physostigmine and pyridostigmine), N-methyl-d-aspartate (NMDA) receptor antagonists (MK-801 and memantine), dual-function NMDA receptor and acetylcholine receptor antagonists (caramiphen and benactyzine) and anti-inflammatory drugs (dexamethasone and ibuprofen). The effects of these drugs on zebrafish survival and the prevalence of abnormal head morphology in the larvae exposed to 4 µM chlorpyrifos oxon [1 × median lethal concentration (LC50)] were determined. Moreover, the neuroprotective effects of pralidoxime, memantine, caramiphen and dexamethasone at the gross morphological level were confirmed by histopathological and transcriptional analyses. Our results demonstrated that the zebrafish model for severe acute OP intoxication has a high predictive value and can be used to identify new compounds that provide neuroprotection against severe acute OP intoxication.
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Kaur S, Singh S, Chahal KS, Prakash A. Potential pharmacological strategies for the improved treatment of organophosphate-induced neurotoxicity. Can J Physiol Pharmacol 2014; 92:893-911. [DOI: 10.1139/cjpp-2014-0113] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Organophosphates (OP) are highly toxic compounds that cause cholinergic neuronal excitotoxicity and dysfunction by irreversible inhibition of acetylcholinesterase, resulting in delayed brain damage. This delayed secondary neuronal destruction, which arises primarily in the cholinergic areas of the brain that contain dense accumulations of cholinergic neurons and the majority of cholinergic projection, could be largely responsible for persistent profound neuropsychiatric and neurological impairments such as memory, cognitive, mental, emotional, motor, and sensory deficits in the victims of OP poisoning. The therapeutic strategies for reducing neuronal brain damage must adopt a multifunctional approach to the various steps of brain deterioration: (i) standard treatment with atropine and related anticholinergic compounds; (ii) anti-excitotoxic therapies to prevent cerebral edema, blockage of calcium influx, inhibition of apoptosis, and allow for the control of seizure; (iii) neuroprotection by aid of antioxidants and N-methyl-d-aspartate (NMDA) antagonists (multifunctional drug therapy), to inhibit/limit the secondary neuronal damage; and (iv) therapies targeting chronic neuropsychiatric and neurological symptoms. These neuroprotective strategies may prevent secondary neuronal damage in both early and late stages of OP poisoning, and thus may be a beneficial approach to treating the neuropsychological and neuronal impairments resulting from OP toxicity.
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Affiliation(s)
- Shamsherjit Kaur
- Department of Pharmacology, ISF College of Pharmacy, Moga 142001, Punjab, India
- Punjab Technical University, Kapurthala 144601, Punjab, India
| | - Satinderpal Singh
- Department of Pharmacology, ISF College of Pharmacy, Moga 142001, Punjab, India
| | - Karan Singh Chahal
- Department of Pharmacology, ISF College of Pharmacy, Moga 142001, Punjab, India
| | - Atish Prakash
- Department of Pharmacology, ISF College of Pharmacy, Moga 142001, Punjab, India
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Anticonvulsant effect of Diazoxide against Dichlorvos-induced seizures in mice. ScientificWorldJournal 2013; 2013:697305. [PMID: 24453891 PMCID: PMC3877645 DOI: 10.1155/2013/697305] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 09/15/2013] [Indexed: 11/30/2022] Open
Abstract
Dichlorvos, a synthetic organophosphate toxin, is used as pesticides. These toxins can be used as pesticides in farming and medicine for the devastation and/or elimination of ectoparasites of animals. Reports have shown that Dichlorvos generate seizure effects in various animals. Potassium channel opener is extensively used for medication of cardiovascular and other diseases. Studies have shown that potassium channel opener has anticonvulsant effects in different animal models. The goal of this study was to evaluate the effect of dizoxide on Dichlorvos-induced seizures in mice. In this research, the animals received different doses of Diazoxide (1, 2.5, 5, 10, and 20 mg/kg b.wt.) intraperitoneally 30 min before intraperitoneal injection of Dichlorvos (50 mg/kg b.w.t). After Dichlorvos injection, latency of clones, severity of seizure, and finally death as the fate were investigated. Results showed that Diazoxide dose-dependently decreased the severity of Dichlorvos-induced seizures, so that Diazoxide at a dose of 5 mg (the lowest, P < 0.05) and 20 mg/kg b.wt. (the highest, P < 0.001) has anticonvulsant effects. Thus, our data suggest that diazoxide as ATP-sensitive potassium channels opener has anticonvulsant activity against dichlorvas-induced seizure.
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Dorandeu F, Dhote F, Barbier L, Baccus B, Testylier G. Treatment of status epilepticus with ketamine, are we there yet? CNS Neurosci Ther 2013; 19:411-27. [PMID: 23601960 PMCID: PMC6493567 DOI: 10.1111/cns.12096] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2012] [Revised: 02/23/2013] [Accepted: 02/23/2013] [Indexed: 12/24/2022] Open
Abstract
Status epilepticus (SE), a neurological emergency both in adults and in children, could lead to brain damage and even death if untreated. Generalized convulsive SE (GCSE) is the most common and severe form, an example of which is that induced by organophosphorus nerve agents. First- and second-line pharmacotherapies are relatively consensual, but if seizures are still not controlled, there is currently no definitive data to guide the optimal choice of therapy. The medical community seems largely reluctant to use ketamine, a noncompetitive antagonist of the N-methyl-d-aspartate glutamate receptor. However, a review of the literature clearly shows that ketamine possesses, in preclinical studies, antiepileptic properties and provides neuroprotection. Clinical evidences are scarcer and more difficult to analyze, owing to a use in situations of polytherapy. In absence of existing or planned randomized clinical trials, the medical community should make up its mind from well-conducted preclinical studies performed on appropriate models. Although potentially active, ketamine has no real place for the treatment of isolated seizures, better accepted drugs being used. Its best usage should be during GCSE, but not waiting for SE to become totally refractory. Concerns about possible developmental neurotoxicity might limit its pediatric use for refractory SE.
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Affiliation(s)
- Frederic Dorandeu
- Département de Toxicologie et risques chimiques, Institut de Recherche Biomédicale des Armées - Centre de Recherches du Service de Santé des Armées (IRBA-CRSSA), La Tronche Cedex, France.
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Multifunctional drugs as novel antidotes for organophosphates’ poisoning. Toxicology 2011; 290:149-55. [DOI: 10.1016/j.tox.2011.09.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 09/17/2011] [Accepted: 09/19/2011] [Indexed: 11/21/2022]
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Ghasemi M, Schachter SC. The NMDA receptor complex as a therapeutic target in epilepsy: a review. Epilepsy Behav 2011; 22:617-40. [PMID: 22056342 DOI: 10.1016/j.yebeh.2011.07.024] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 07/01/2011] [Accepted: 07/18/2011] [Indexed: 01/02/2023]
Abstract
A substantial amount of research has shown that N-methyl-D-aspartate receptors (NMDARs) may play a key role in the pathophysiology of several neurological diseases, including epilepsy. Animal models of epilepsy and clinical studies demonstrate that NMDAR activity and expression can be altered in association with epilepsy and particularly in some specific seizure types. NMDAR antagonists have been shown to have antiepileptic effects in both clinical and preclinical studies. There is some evidence that conventional antiepileptic drugs may also affect NMDAR function. In this review, we describe the evidence for the involvement of NMDARs in the pathophysiology of epilepsy and provide an overview of NMDAR antagonists that have been investigated in clinical trials and animal models of epilepsy.
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Affiliation(s)
- Mehdi Ghasemi
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Gao Y, Payne RS, Schurr A, Hougland T, Lord J, Herman L, Lei Z, Banerjee P, El-Mallakh RS. Memantine reduces mania-like symptoms in animal models. Psychiatry Res 2011; 188:366-71. [PMID: 21269711 DOI: 10.1016/j.psychres.2010.12.030] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2010] [Revised: 12/18/2010] [Accepted: 12/20/2010] [Indexed: 01/04/2023]
Abstract
Memantine, a selective antagonist of the N-methyl-D-aspartate receptor, is approved for the treatment of moderate to severe Alzheimer's disease. Ion dysregulation is thought to be involved in the pathophysiology of bipolar illness, suggesting that memantine may be effective in treating bipolar manic and/or depressive episodes. We utilized two preclinical models of mania that mimic pathophysiologic changes seen in bipolar illness to examine the potential efficacy of memantine in the treatment of this disorder. Locomotor hyperactivity of male Sprague-Dawley rats in an open field was induced with intracerebroventricular (ICV) administration of 10(-3) M ouabain. Memantine (2.5, 5 or 7.5mg/kg), lithium (6.75 mEq/kg), or vehicle were administered acutely via intraperitoneal injection immediately prior to ouabain, then chronically for 7 days (oral memantine 20, 30, and 40 mg/kg/day in water; lithium 2.4 g/kg food). In a second model of bipolar disorder, cycling between population spikes and epileptiform bursts was investigated in rat hippocampal slices treated with ouabain (3.3 μM) alone or in combination with memantine (0.5, 1.0, and 5.0 μM). Ouabain-induced hyperlocomotion was normalized with acute and chronic lithium and chronic use of memantine. Memantine delayed the onset of ouabain-induced-cycling in hippocampal slices. Memantine may have antimanic properties.
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Affiliation(s)
- Yonglin Gao
- Mood Disorders Research Program, Department of Psychiatry and Behavioral Sciences, University of Louisville School of Medicine, Louisville, KY 40202, United States
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Roy M, Castro-Lionard K, Crawford-Achour E, Desseigne N, Beyens MN, Guy C, Imler D, Cornillon D. Les médicaments à visée anti-Alzheimer favorisent-ils la survenue de crises d’épilepsie ? Discussion à propos de 3 cas cliniques. Therapie 2011. [DOI: 10.2515/therapie/2011038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Aracava Y, Pereira EFR, Akkerman M, Adler M, Albuquerque EX. Effectiveness of donepezil, rivastigmine, and (+/-)huperzine A in counteracting the acute toxicity of organophosphorus nerve agents: comparison with galantamine. J Pharmacol Exp Ther 2009; 331:1014-24. [PMID: 19741148 DOI: 10.1124/jpet.109.160028] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Galantamine, a centrally acting cholinesterase (ChE) inhibitor and a nicotinic allosteric potentiating ligand used to treat Alzheimer's disease, is an effective and safe antidote against poisoning with nerve agents, including soman. Here, the effectiveness of galantamine was compared with that of the centrally active ChE inhibitors donepezil, rivastigmine, and (+/-)huperzine A as a pre- and/or post-treatment to counteract the acute toxicity of soman. In the first set of experiments, male prepubertal guinea pigs were treated intramuscularly with one of the test drugs and 30 min later challenged with 1.5 x LD(50) soman (42 microg/kg s.c.). All animals that were pretreated with galantamine (6-8 mg/kg), 3 mg/kg donepezil, 6 mg/kg rivastigmine, or 0.3 mg/kg (+/-)huperzine A survived the soman challenge, provided that they were also post-treated with atropine (10 mg/kg i.m.). However, only galantamine was well tolerated. In subsequent experiments, the effectiveness of specific treatment regimens using 8 mg/kg galantamine, 3 mg/kg donepezil, 6 mg/kg rivastigmine, or 0.3 mg/kg (+/-)huperzine A was compared in guinea pigs challenged with soman. In the absence of atropine, only galantamine worked as an effective and safe pretreatment in animals challenged with 1.0 x LD(50) soman. Galantamine was also the only drug to afford significant protection when given to guinea pigs after 1.0 x LD(50) soman. Finally, all test drugs except galantamine reduced the survival of the animals when administered 1 or 3 h after the challenge with 0.6 or 0.7 x LD(50) soman. Thus, galantamine emerges as a superior antidotal therapy against the toxicity of soman.
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Affiliation(s)
- Yasco Aracava
- Department of Pharmacology and Experimental Therapeutics, University of Maryland School of Medicine, Baltimore, Maryland, USA
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Schneider BM, Dodman NH, Faissler D, Ogata N. Clinical use of an herbal-derived compound (Huperzine A) to treat putative complex partial seizures in a dog. Epilepsy Behav 2009; 15:529-34. [PMID: 19616481 DOI: 10.1016/j.yebeh.2009.06.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 06/03/2009] [Accepted: 06/07/2009] [Indexed: 10/20/2022]
Abstract
A Bernese mountain dog was diagnosed with complex partial seizures that were supported by electroencephalographic findings. Clinical signs of the problem included "star gazing," fly snapping, licking, vacuous chewing, and ongoing anxiety. Treatment with Huperzine A, a compound isolated from Chinese club moss with NMDA receptor blocking activity, anticholinesterase activity, and anticonvulsant properties, produced useful suppression of the abnormal behavior for more than months. A relapse occurred when the dog was treated with tramadol for joint pain and the improvement that had been made was not recaptured with Huperzine A. At this stage, phenobarbital therapy was instituted and the dog improved greatly. The role of Huperzine A in controlling seizures is discussed.
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Affiliation(s)
- Barbara M Schneider
- Clinical Sciences Department, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA, USA
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Zaja-Milatovic S, Gupta RC, Aschner M, Milatovic D. Protection of DFP-induced oxidative damage and neurodegeneration by antioxidants and NMDA receptor antagonist. Toxicol Appl Pharmacol 2009; 240:124-31. [PMID: 19615394 DOI: 10.1016/j.taap.2009.07.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2009] [Revised: 07/02/2009] [Accepted: 07/06/2009] [Indexed: 12/20/2022]
Abstract
Prophylactic agents acutely administered in response to anticholinesterases intoxication can prevent toxic symptoms, including fasciculations, seizures, convulsions and death. However, anticholinesterases also have long-term unknown pathophysiological effects, making rational prophylaxis/treatment problematic. Increasing evidence suggests that in addition to excessive cholinergic stimulation, organophosphate compounds such as diisopropylphosphorofluoridate (DFP) induce activation of glutamatergic neurons, generation of reactive oxygen (ROS) and nitrogen species (RNS), leading to neurodegeneration. The present study investigated multiple affectors of DFP exposure critical to cerebral oxidative damage and whether antioxidants and NMDA receptor antagonist memantine provide neuroprotection by preventing DFP-induced biochemical and morphometric changes in rat brain. Rats treated acutely with DFP (1.25 mg/kg, s.c.) developed onset of toxicity signs within 7-15 min that progressed to maximal severity of seizures and fasciculations within 60 min. At this time point, DFP caused significant (p<0.01) increases in biomarkers of ROS (F2-isoprostanes, F2-IsoPs; and F4-neuroprostanes, F4-NeuroPs), RNS (citrulline), and declines in high-energy phosphates (HEP) in rat cerebrum. At the same time, quantitative morphometric analysis of pyramidal neurons of the hippocampal CA1 region revealed significant (p<0.01) reductions in dendritic lengths and spine density. When rats were pretreated with the antioxidants N-tert-butyl-alpha-phenylnitrone (PBN, 200 mg/kg, i.p.), or vitamin E (100 mg/kg, i.p./day for 3 days), or memantine (18 mg/kg, i.p.), significant attenuations in DFP-induced increases in F2-IsoPs, F4-NeuroPs, citrulline, and depletion of HEP were noted. Furthermore, attenuation in oxidative damage following antioxidants or memantine pretreatment was accompanied by rescue from dendritic degeneration of pyramidal neurons in the CA1 hippocampal area. These findings closely associated DFP-induced lipid peroxidation with dendritic degeneration of pyramidal neurons in the CA1 hippocampal area and point to possible interventions to limit oxidative injury and dendritic degeneration induced by anticholinesterase neurotoxicity.
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Affiliation(s)
- Snjezana Zaja-Milatovic
- Vanderbilt University School of Medicine, Department of Pediatrics/Pediatric Toxicology, Nashville, TN 37232-0414, USA
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Weissman BA, Raveh L. Therapy against organophosphate poisoning: The importance of anticholinergic drugs with antiglutamatergic properties. Toxicol Appl Pharmacol 2008; 232:351-8. [DOI: 10.1016/j.taap.2008.07.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 06/23/2008] [Accepted: 07/07/2008] [Indexed: 10/21/2022]
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NMDA antagonists exert distinct effects in experimental organophosphate or carbamate poisoning in mice. Toxicol Appl Pharmacol 2007; 219:114-21. [DOI: 10.1016/j.taap.2006.10.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2006] [Revised: 10/29/2006] [Accepted: 10/30/2006] [Indexed: 11/18/2022]
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25
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Neuronal oxidative injury and dendritic damage induced by carbofuran: protection by memantine. Toxicol Appl Pharmacol 2006; 219:97-105. [PMID: 17188316 DOI: 10.1016/j.taap.2006.10.028] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Revised: 10/23/2006] [Accepted: 10/27/2006] [Indexed: 11/25/2022]
Abstract
Carbamate insecticides mediate their neurotoxicity by acetylcholinesterase (AChE) inactivation. Male Sprague-Dawley rats acutely intoxicated with the carbamate insecticide carbofuran (1.5 mg/kg, sc) developed hypercholinergic signs within 5-7 min of exposure, with maximal severity characterized by seizures within 30-60 min, lasting for about 2 h. At the time of peak severity, compared with controls, AChE was maximally inhibited (by 82-90%), radical oxygen species (ROS) markers (F(2)-isoprostanes, F(2)-IsoPs; and F(4)-neuroprostanes, F(4)-NeuroPs) were elevated 2- to 3-fold, and the radical nitrogen species (RNS) marker citrulline was elevated 4- to 8-fold in discrete brain regions (cortex, amygdala, and hippocampus). In addition, levels of high-energy phosphates (HEPs) were significantly reduced (ATP, by 43-56%; and phosphocreatine, by 37-48%). Values of total adenine nucleotides and total creatine compounds declined markedly (by 41-56% and 35-45%, respectively), while energy charge potential remained unchanged. Quantitative morphometric analysis of pyramidal neurons of the hippocampal CA1 region revealed significant decreases in dendritic lengths (by 64%) and spine density (by 60%). Pretreatment with the N-methyl-D-aspartate (NMDA) receptor antagonist memantine (18 mg/kg, sc), in combination with atropine sulfate (16 mg/kg, sc), significantly attenuated carbofuran-induced changes in AChE activity and levels of F(2)-IsoPs and F(4)-NeuroPs, declines in HEPs, as well as the alterations in morphology of hippocampal neurons. MEM and ATS pretreatment also protected rats from carbofuran-induced hypercholinergic behavioral activity, including seizures. These findings support the involvement of ROS and RNS in seizure-induced neuronal injury and suggest that memantine by preventing carbofuran-induced neuronal hyperactivity blocks pathways associated with oxidative damage in neurons.
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Svensson I, Waara L, Cassel G. Effects of HI 6, diazepam and atropine on soman-induced IL-1 beta protein in rat brain. Neurotoxicology 2005; 26:173-81. [PMID: 15713338 DOI: 10.1016/j.neuro.2004.11.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2004] [Accepted: 11/04/2004] [Indexed: 11/22/2022]
Abstract
The current treatment for soman-intoxication is the oxime HI 6 together with the anticholinergic drug atropine. This antidote combination is known to have effects on seizures, respiratory system, blood pressure and animal survival in experiments. However, the inflammatory responses following soman-intoxication leading to neuronal damage have not been fully evaluated. In this paper we focus on the cytokine IL-1beta induction in the rat brain after soman-intoxication (1.0 x LD50 and 1.1 x LD50) and during antidote treatment. We analyzed the IL-1beta levels in rat brain to determine the effects of time of antidote HI 6 and atropine; the effects of different combinations of HI 6 and atropine; and also the effects of antidotes diazepam and atropine following soman-intoxication. We observed that the initiation of the antidote combination of HI 6 and atropine following soman-intoxication was crucial for successful treatment. The study also demonstrated that atropine alone was more effective against IL-1beta up-regulation after soman-intoxication within the 2-h time frame, than the combination of the HI 6 and atropine, the therapy of choice in many countries. Furthermore, treatment with a combination of diazepam and atropine maintained IL-1beta levels at normal when administered at the onset of the seizures following soman exposure. Soman-intoxicated groups without seizures did not have an elevated cytokine level. This corroborates our earlier studies where soman-intoxicated animals with seizures had high levels of IL-1beta, while animals without seizures had normal values. Our results show that both time and the antidote regime are crucial to the success of treatment.
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Affiliation(s)
- I Svensson
- Swedish Defence Research Agency, Division of NBC Defence, SE-901 82 Umeå, Sweden.
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Zhou Z, Dai X, Gu X, Sun Y, Zheng G, Zheng J. Memantine Alleviates Toxicity Induced by Dichlorvos in Rats. J Occup Health 2005; 47:96-101. [PMID: 15824473 DOI: 10.1539/joh.47.96] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The changes of N-methyl-D-aspartate (NMDA) receptor and protective efficacy of memantine (MEM) in rats poisoned with dichlorvos were studied. Dichlorvos evoked down-regulation of the affinity and density of [(3)H]MK-801 binding to NMDA receptor in the brain of rats receiving dichlorvos (15 and 25 mg/kg bw, i.p.). The binding capacity of NMDA receptor and acetylcholinesterase activity were determined at 4 h, 8 h, 16 h, 24 h and 48 h after treatment. When rats were given a different doses of MEM (5, 15 and 45 mg/kg bw) after poisoning (dichlorvos 25 mg/kg bw), the latency of onset of signs was postponed and the magnitude of muscular fasciculation was alleviated as the dose of MEM increased. The lower doses of MEM (5 and 15 mg/kg bw) could antagonize the dichlorvos-evoked down-regulation of NMDA receptor, while the highest dose (45 mg/kg bw) decreased the Bmax and Kd values of NMDA receptors. These results show the dichlorvos-evoked down-regulation of NMDA receptor might be self-regulation by the body to protect the central nervous system. MEM could antagonize the down-regulation of NMDA receptors, and alleviated signs of poisoning, especially reducing the magnitude of muscular fasciculation. We suggest that the role of NMDA receptor in organophosphates (OP) poisoning should receive more attention, and, that MEM treatment in acute OP poisoning, as a supplement to atropine and oxime, should be considered.
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Affiliation(s)
- Zhijun Zhou
- School of Public Health, Fudan University, China.
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Milatovic D, Gupta RC, Dekundy A, Montine TJ, Dettbarn WD. Carbofuran-induced oxidative stress in slow and fast skeletal muscles: prevention by memantine and atropine. Toxicology 2005; 208:13-24. [PMID: 15664429 DOI: 10.1016/j.tox.2004.11.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Revised: 10/29/2004] [Accepted: 11/01/2004] [Indexed: 10/26/2022]
Abstract
Acute toxic effects of acetylcholinesterase (AChE) inhibitors on skeletal muscles are thought to involve oxidative stress with increased generation of free radicals such as reactive oxygen species (ROS) and reactive nitrogen species (RNS). Muscle hyperactivity with its increased oxygen and energy consumption appear to be the primary cause of oxidative stress. The present investigation was therefore undertaken to establish the normal levels of F(2)-isoprostanes (F(2)-IsoPs, specific markers of ROS/oxidative stress), citrulline (determinant of NO/NOS and marker of RNS), and high-energy phosphates (HEP: adenosine triphosphate, ATP and phosphocreatine, PCr) in slow (soleus) and fast (extensor digitorum longus, EDL) muscles of rats. In addition, we aimed to determine if memantine HCl (MEM), in combination with atropine sulfate (ATS), prevents carbofuran-induced changes in markers of oxidative stress. Control values were not significantly different for F(2)-IsoPs (1.142 +/- 0.027 and 1.177 +/- 0.092 ng/g) and citrulline (469.7 +/- 31.8 and 417.8 +/- 18.5 nmol/g) in soleus and EDL muscles, while the values were different for HEP (ATP, 3.66 +/- 0.11 and 5.85 +/- 0.14 micromol/g; PCr, 7.91 +/- 0.26 and 13.14 +/- 0.31 micromol/g). Rats acutely intoxicated with carbofuran (1.5 mg/kg, s.c.) showed the signs of maximal toxicity including muscle hyperactivity within 60 min of exposure. At this time, F(2)-IsoPs (177 and 153%) and citrulline (267 and 304%) levels were significantly increased, while ATP (46 and 43%) and PCr (44 and 46%) levels were decreased in soleus and EDL, respectively. Rats pretreated with MEM (18 mg/kg, s.c.) and ATS (16 mg/kg, s.c.), 60 and 15 min prior to carbofuran, respectively, showed no signs of toxicity. MEM in combination with ATS protected muscles from carbofuran-induced hyperactivity and attenuated increases in F(2)-IsoPs and citrulline, and depletion of HEP. Carbofuran-induced changes and protection by MEM and ATS were of similar magnitude in both muscles. These findings indicate that carbofuran-induced muscle hyperactivity produces oxidative stress as measured by increased ROS and RNS generation, and HEP depletion. MEM and ATS prevent the carbofuran-induced chain of events involved in oxidative stress.
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Gupta RC, Dekundy A. Memantine does not influence AChE inhibition in rat brain by donepezil or rivastigmine but does with DFP and metrifonate in in vivo studies. Drug Dev Res 2005. [DOI: 10.1002/ddr.10422] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Enz A, Gentsch C. Co-administration of memantine has no effect on the in vitro or ex vivo determined acetylcholinesterase inhibition of rivastigmine in the rat brain. Neuropharmacology 2004; 47:408-13. [PMID: 15275830 DOI: 10.1016/j.neuropharm.2004.04.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2004] [Revised: 04/02/2004] [Accepted: 04/22/2004] [Indexed: 10/26/2022]
Abstract
Rivastigmine, a cholinesterase inhibitor, is successfully used for the symptomatic therapy of Alzheimer's disease (AD) in the clinic. The drug has a very low potential for drug-drug interactions, as has been demonstrated within large clinical trials. Memantine, recently approved by the FDA for the treatment of moderate to severe AD, acts as a low affinity, non-competitive NMDA-antagonist, on a completely different neurotransmitter system, the glutamatergic system. Given the different sites of action, the possibility to combine a cholinergic with a glutamatergic intervention as potentially superior AD therapy has recently been proposed. In vitro studies have demonstrated that memantine, when added to reversible AChE inhibitors, such as tacrine, donepezil or galantamine, did not interfere with the inhibitory action of any of these drugs. The results from the present study provide evidence that rivastigmine as a pseudo-irreversible (or slow-reversible) AChE inhibitor shares this property described for reversible inhibitors, since memantine (1-100 microM), irrespective of whether given prior to or after rivastigmine did not influence rivastigmine's AChE inhibition in vitro. A similar observation was also made under in vivo conditions (ex vivo measurements): following a 21 day chronic, oral administration of 6 micromol/kg rivastigmine alone or of a combination of rivastigmine plus memantine (6 micromol/kg p.o. of either of the two compounds), an identical degree of AChE inhibition was observed. The concentrations of rivastigmine, its metabolite NAP 226-90 and memantine were measured in the brain of the same animals. Following an equimolar oral dose (6 micromol/kg) of both compounds, the brain level of memantine exceeded that of rivastigmine + metabolite, by a factor of around 30, when measured 2 h after the final dosing, irrespective of the duration of treatment (acute, for 3 or 21 days). This indicates that neither of the two drugs showed accumulation but also, and more importantly, that memantine does not modulate the prime therapeutic action of rivastigmine (AChE inhibition) in vitro or in vivo. Clinical trials using a combination of both drugs will provide a final proof of whether a combination therapy would lead to an increased efficacy in AD patients.
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Affiliation(s)
- Albert Enz
- Neuroscience Disease Area, Department of Neuroscience, Novartis Institutes for Biomedical Research, WSJ-386.762, CH-4002 Basel, Switzerland.
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Peterson SL, Purvis RS, Griffith JW. Differential Neuroprotective Effects of the NMDA Receptor-Associated Glycine Site Partial Agonists 1-Aminocyclopropanecarboxylic Acid (ACPC) and d-Cycloserine in Lithium-Pilocarpine Status Epilepticus. Neurotoxicology 2004; 25:835-47. [PMID: 15288514 DOI: 10.1016/j.neuro.2004.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2003] [Accepted: 01/13/2004] [Indexed: 11/30/2022]
Abstract
The status epilepticus (SE) induced in rats by lithium-pilocarpine (Li-pilo) shares many common features with soman-induced SE including a glutamatergic phase that is inhibited by NMDA antagonists. The present study determined whether 1-aminocyclopropanecarboxylic acid (ACPC) or D-cycloserine (DCS), both partial agonists of the strychnine-insensitive glycine site on the NMDA receptor ionophore complex, exerted anticonvulsant or neuroprotectant activity in Li-pilo SE. ACPC or DCS were administered either immediately following pilocarpine (exposure treatment) or 5 min after the onset of SE as determined by ECoG activity. SE was allowed to proceed for 3 h before termination with propofol. The rats were sacrificed 24 h following pilocarpine administration. Neither drug had an effect on the latency to seizure onset or the duration of seizure activity. ACPC administered 5 min after SE onset produced significant neuroprotection in cortical regions, amygdala and CA1 of the hippocampus. In contrast, when administered as exposure treatment ACPC enhanced the neural damage in the thalamus and CA3 of the hippocampus suggesting the neuropathology in those regions is mediated by a different subset of NMDA receptors. DCS had no neuroprotectant activity in Li-pilo SE but exacerbated neuronal damage in the thalamus. Neither drug affected the cholinergic convulsions but both had differential effects on neural damage. This suggests that the SE-induced seizure activity and subsequent neuronal damage involve independent mechanisms.
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Affiliation(s)
- Steven L Peterson
- College of Pharmacy, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA.
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Wenk GL, Quack G, Moebius HJ, Danysz W. No interaction of memantine with acetylcholinesterase inhibitors approved for clinical use. Life Sci 2000; 66:1079-83. [PMID: 10737358 DOI: 10.1016/s0024-3205(00)00411-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The loss of cholinergic neurons within the basal forebrain of patients with Alzheimer's disease (AD) may underlie aspects of the dementia. Excessive activation of N-methyl-D-aspartate (NMDA) receptors may underlie the degeneration of cholinergic cells. New drug therapies have been designed to either enhance cholinergic function by inhibition acetylcholinesterase (AChE), e.g. galanthamine, tetrahydroaminoacridine or donepezil, or by attenuation of NMDA receptor function, e.g. memantine. A combination of these two therapeutic approaches may be more beneficial at slowing the progression of the AD. The current study investigated whether memantine would attenuate the inhibition of AChE produced by these three drugs. The results indicate that these AChE inhibitors do not lose their therapeutic efficacy in combination with memantine. Our in vitro data suggest that the clinical combination of memantine with a reversible AChE inhibitor should be a valuable pharmacotherapeutic approach to dementia.
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Affiliation(s)
- G L Wenk
- Division of Neural Systems, Memory & Aging, University of Arizona, Tucson 85724, USA.
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Zivin M, Milatovic D, Dettbarn WD. Nitrone spin trapping compound N-tert-butyl-alpha-phenylnitrone prevents seizures induced by anticholinesterases. Brain Res 1999; 850:63-72. [PMID: 10629749 DOI: 10.1016/s0006-8993(99)02101-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The neuroprotection afforded by spin trapping agents such as N-tert-butyl-alpha-phenylnitrone (PBN) has lent support to the hypothesis that increased production of reactive oxygen species (ROS) is a major contributing factor to excitotoxicity, aging and cognitive decline. Little is known, however, about the pharmacological properties of PBN. We have compared the acute effects of PBN on the development of seizures induced by the irreversible acetylcholinesterase (AChE) inhibitor diisopropylphosphorofluoridate (DFP), the reversible AChE inhibitor physostigmine (PHY), the muscarinic cholinergic receptor agonist pilocarpine (PIL) and the glutamatergic receptor agonist kainic acid (KA). Rats were sacrificed 90 min after the injection of seizure-inducing agents. In situ hybridization was used to detect the induction of immediate early gene (IEG) c-fos and c-jun mRNA's and the levels of AChE mRNA. The activity of AChE was visualized by AChE staining and quantified using an in vitro AChE assay. The seizures correlated with the induction of IEG mRNA's with all agents used. The pre-treatment with 150 mg/kg of PBN prevented DFP- and PHY-induced seizures and the related expression of IEG mRNA's, but had no effect on PIL- or KA-induced seizures and associated IEG mRNA's changes. PBN prevented seizures and significantly protected AChE activity against DFP inhibition when given before, but not when given after DFP. This study shows that PBN specifically protects against anticholinesterase-induced seizures by reversible protection of AChE activity and not by the blockade of muscarinic or glutamate receptors, reactivation of AChE or scavenging of ROS. The anticholinesterase properties should be considered when using PBN in studies of cholinergic dysfunction.
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Affiliation(s)
- M Zivin
- Institute of Pathophysiology, University of Ljubljana, Medical School, Slovenia
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Parsons CG, Danysz W, Quack G. Memantine is a clinically well tolerated N-methyl-D-aspartate (NMDA) receptor antagonist--a review of preclinical data. Neuropharmacology 1999; 38:735-67. [PMID: 10465680 DOI: 10.1016/s0028-3908(99)00019-2] [Citation(s) in RCA: 674] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
N-methyl-D-aspartate (NMDA) receptor antagonists have therapeutic potential in numerous CNS disorders ranging from acute neurodegeneration (e.g. stroke and trauma), chronic neurodegeneration (e.g. Parkinson's disease, Alzheimer's disease, Huntington's disease, ALS) to symptomatic treatment (e.g. epilepsy, Parkinson's disease, drug dependence, depression, anxiety and chronic pain). However, many NMDA receptor antagonists also produce highly undesirable side effects at doses within their putative therapeutic range. This has unfortunately led to the conclusion that NMDA receptor antagonism is not a valid therapeutic approach. However, memantine is clearly an uncompetitive NMDA receptor antagonist at therapeutic concentrations achieved in the treatment of dementia and is essentially devoid of such side effects at doses within the therapeutic range. This has been attributed to memantine's moderate potency and associated rapid, strongly voltage-dependent blocking kinetics. The aim of this review is to summarise preclinical data on memantine supporting its mechanism of action and promising profile in animal models of chronic neurodegenerative diseases. The ultimate purpose is to provide evidence that it is indeed possible to develop clinically well tolerated NMDA receptor antagonists, a fact reflected in the recent interest of several pharmaceutical companies in developing compounds with similar properties to memantine.
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Affiliation(s)
- C G Parsons
- Department of Pharmacological Research, Merz and Co., Frankfurt am Main, Germany.
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35
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Abstract
This report describes studies of anticonvulsants for the organophosphorus (OP) nerve agent soman: a basic research effort to understand how different pharmacological classes of compounds influence the expression of seizure produced by soman in rats, and a drug screening effort to determine whether clinically useful antiepileptics can modulate soman-induced seizures in rats. Electroencephalographic (EEG) recordings were used in these studies. Basic studies were conducted in rats pretreated with HI-6 and challenged with 1.6 x LD50 soman. Antimuscarinic compounds were extremely effective in blocking (pretreatment) or terminating soman seizures when given 5 min after seizure onset. However, significantly higher doses were required when treatment was delayed for more than 10 min, and some antimuscarinic compounds lost anticonvulsant efficacy when treatment was delayed for more than 40 min. Diazepam blocked seizure onset, yet seizures could recur after an initial period of anticonvulsant effect at doses </=2.5 mg/kg. Diazepam could terminate ongoing seizures when given 5 min after seizure onset, but doses up to 20 mg/kg were ineffective when treatment was delayed for 40 min. The GABA uptake inhibitor, tiagabine, was ineffective in blocking or terminating soman motor convulsions or seizures. The glutamate receptor antagonists, NBQX, GYKI 52466, and memantine, had weak or minimal antiseizure activity, even at doses that virtually eliminated signs of motor convulsions. The antinicotinic, mecamylamine, was ineffective in blocking or stopping seizure activity. Pretreatment with a narrow range of doses of alpha2-adrenergic agonist, clonidine, produced variable protection (40-60%) against seizure onset; treatment after seizure onset with clonidine was not effective. Screening studies in rats, using HI-6 pretreatment, showed that benzodiazepines (diazepam, midazolam and lorazepam) were quite effective when given 5 min after seizure onset, but lost their efficacy when given 40 min after onset. The barbiturate, pentobarbital, was modestly effective in terminating seizures when given 5 or 40 min after seizure onset, while other clinically effective antiepileptic drugs, trimethadione and valproic acid, were only slightly effective when given 5 min after onset. In contrast, phenytoin, carbamazepine, ethosuximide, magnesium sulfate, lamotrigine, primidone, felbamate, acetazolamide, and ketamine were ineffective.
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Affiliation(s)
- T Shih
- Pharmacology and Drug Assessment Divisions, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Md., USA
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36
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Abstract
The optical isomers of the N-methyl-D-aspartate (NMDA) receptor ion-channel blocker dizocilpine (MK-801) were shown to interact with electric eel and rat brain acetylcholinesterase (AChE) in a mixed competitive-noncompetitive way. The (-) form, pharmacologically less active, was the most potent of the two isomers as an AChE inhibitor (Ki for electric eel and rat brain AChE being 6.2 and 17.9 microM, respectively, compared with 200 and 450 microM, respectively, of the (+) form). Both enantiomers premixed with AChE preparations, dose-dependently protected the enzyme from inactivation by diisopropylfluorophosphate (DFP). The maximal protective effects against 40 and 10 microM DFP were in the ranges 10.7-23.8 and 19.5-31.4% of control enzymic activity for the (+) and (-) forms of dizocilpine, respectively. The extent of the protective effect against DFP was increased up to 80.1% of control enzymic activity for (-)-dizocilpine and to 38.4% for (+)-dizocilpine by diluting the enzymic mixtures 1000 times after treatment with the organophosphate agent. The two enantiomers added to AChE 15 min after DFP, failed to reactivate the enzyme. Finally, it was shown that (+)- and (-)-dizocilpine dose-dependently and competitively decreased the DFP bimolecular reaction constant, K(i). We conclude that dizocilpine exerts a protective action towards AChE against irreversible DFP inhibition, but the molecular mechanism of such an action is at present unclear.
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Affiliation(s)
- A Galli
- Dipartimento di Farmacologia Preclinica e Clinica, Università di Firenze, Italy
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Deshpande SS, Smith CD, Filbert MG. Assessment of primary neuronal culture as a model for soman-induced neurotoxicity and effectiveness of memantine as a neuroprotective drug. Arch Toxicol 1995; 69:384-90. [PMID: 7495376 DOI: 10.1007/s002040050188] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
An in vitro mammalian model neuronal system to evaluate the intrinsic toxicity of soman and other neurotoxicants as well as the efficacy of potential countermeasures was investigated. The link between soman toxicity, glutamate hyperactivity and neuronal death in the central nervous system was investigated in primary dissociated cell cultures from rat hippocampus and cerebral neocortex. Exposure of cortical or hippocampal neurons to glutamate for 30 min produced neuronal death in almost 80% of the cells examined at 24 h. Hippocampal neurons exposed to soman for 15-120 min at 0.1 microM concentration caused almost complete inhibition (> or = 90%) of acetylcholinesterase but failed to show any evidence of effects on cell viability, indicating a lack of direct cytotoxicity by this agent. Acetylcholine (ACh, 0.1 mM), alone or in combination with soman, did not potentiate glutamate toxicity in hippocampal neurons. Memantine, a drug used for the therapy of Parkinson's disease, spasticity and other brain disorders, significantly protected hippocampal and cortical neurons in culture against glutamate and N-methyl-D-aspartate (NMDA) excitotoxicity. In rats a single dose of memantine (18 mg/kg) administered 1 h prior to a s.c. injection of a 0.9 LD50 dose of soman reduced the severity of convulsions and increased survival. Survival, however, was accompanied by neuronal loss in the frontal cortex, piriform cortex and hippocampus.
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Affiliation(s)
- S S Deshpande
- Neurotoxicology Branch, USAMRICD, Aberdeen Proving Ground, MD 21010-5425, USA
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Apland JP, Cann FJ. Anticonvulsant effects of memantine and MK-801 in guinea pig hippocampal slices. Brain Res Bull 1995; 37:311-6. [PMID: 7627576 DOI: 10.1016/0361-9230(95)00038-g] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The anticonvulsant properties of memantine (Mem) were compared to those of MK-801. Extracellular field recordings were obtained from area CA1 of guinea pig hippocampal slices in a total submersion chamber at 32 degrees C in normal oxygenated artificial cerebrospinal fluid (ACSF). Evoked responses were elicited by 0.07 Hz stimulation of the Schaffer collateral and commissural fibers. Bath perfusion of slices with Mg(2+)-free ACSF and N-methyl-D-aspartate (NMDA)-containing ACSF induced epileptiform afterdischarges following evoked responses. Pretreatment of slices by bath application of 100 microM Mem for 18-20 min prevented epileptiform afterdischarges under both convulsant conditions. Perfusion with 100 microM Mem alone for up to 50 min had no discernible effect on evoked responses. MK-801 was as effective at < or = 10 microM and required application for over 15 min to suppress afterdischarges completely. Both Mem and MK-801 suppressed epileptiform activity when applied after such activity was induced by NMDA or MG(2+)-free ACSF. The EC50 of Mem was 16.6 microM and that of MK-801 was 0.19 microM for blocking NMDA-induced evoked response suppression. Thus, in the guinea pig hippocampal slice preparation, Mem appeared to have anticonvulsant properties qualitatively similar to those of MK-801, but was 10-100 fold less potent.
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Affiliation(s)
- J P Apland
- Neurotoxicology Branch, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5425, USA
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Abstract
Carbofuran, an anticholinesterase carbamate, is commonly used as an insecticide, nematicide, and acaricide in agricultural practice throughout the world. Due to its widespread use in agriculture, contamination of food, water, and air has become imminent, and consequently adverse health effects are inevitable in humans, animals, wildlife, and fish. Currently, carbofuran's involvement is most frequently encountered in malicious poisoning. The literature on chemical properties, acute toxicity data, poisoning incidences, pharmacokinetics, and mechanism of toxicity of carbofuran is briefly reviewed. Much emphasis is given to the metabolism of carbofuran, and the impact of carbofuran and its two major metabolites (3-hydroxycarbofuran and 3-ketocarbofuran) on overall toxicity. Biochemical (cholinergic and noncholinergic), hematological, and immunological effects induced by carbofuran are discussed in detail. Carbofuran and/or its major metabolites can cross the placental barrier and produce serious effects on the maternal-placental-fetal unit. Carbofuran's toxicity can be potentiated by simultaneous exposure with other cholinesterase inhibitors. Literature on various biomarkers of carbofuran exposure and on induced adverse health effects is also presented. To date, a combination of atropine and memantine remains the most effective antidotal treatment against acute carbofuran toxicity.
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Affiliation(s)
- R C Gupta
- Toxicology Section, Breathitt Veterinary Center, Murray State University, Hopkinsville, Kentucky 42240
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Eisenberg E, LaCross S, Strassman AM. The effects of the clinically tested NMDA receptor antagonist memantine on carrageenan-induced thermal hyperalgesia in rats. Eur J Pharmacol 1994; 255:123-9. [PMID: 8026538 DOI: 10.1016/0014-2999(94)90090-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
This study tested the prophylactic and the therapeutic efficacy of memantine (1-amino-3,5-dimethyl-amandate), a clinically tested N-methyl-D-aspartate (NMDA) receptor antagonist, in suppressing carrageenan-induced thermal hyperalgesia in rats. Rats were injected with 0.1 ml of 1% carrageenan solution s.c. into the right hindpaw, and exhibited hyperalgesia in the injected paw as evidenced by a significant reduction of withdrawal latencies from baseline 1, 3, 5, and 24 h following carrageenan. Prophylactic injection of memantine, 10 and 15 mg/kg, significantly suppressed the hyperalgesia 1, 3, and 5 h post-carrageenan, with maximal effects of 70% (10 mg/kg) and 90% (15 mg/kg) at 1 h post-carrageenan. Therapeutic injection of 10 mg/kg of memantine (2.5 h post-carrageenan) had no effect. The 15 mg/kg dose produced a small effect (peak of 44%) at 3.5 h but not at a statistically significant level, and had no effect 5 h post-carrageenan. This study provides evidence that memantine produces primarily a prophylactic effect (and has only a tendency to produce a therapeutic effect) on carrageenan-induced hyperalgesia at doses that do not significantly alter other motor behaviors.
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Affiliation(s)
- E Eisenberg
- Department of Neurology, Massachusetts General Hospital, Boston 02129
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Girardi E, Schneider P, Rodriguez De Lores Arnaiz G. Area-specific modification of acetylcholinesterase activity following 3-mercaptopropionic acid-induced seizures. MOLECULAR AND CHEMICAL NEUROPATHOLOGY 1994; 21:13-22. [PMID: 8179769 DOI: 10.1007/bf03160081] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Acetylcholinesterase activity (AChE) was assayed in rat CNS membrane fractions after administration of the convulsant 3-mercaptopropionic acid (150 mg/kg, ip). In comparison with saline-injected controls, total AChE activity decreased 12-20% in striatum and cerebellum during seizure and postseizure but failed to change in cerebral cortex. Specific AChE activity, assayed in the presence of 10(-4) M ethopropazine (a butyrylcholinesterase inhibitor), decreased 15-25% in striatum and cerebellum, increased 20-45% in hippocampus, but remained unchanged in cerebral cortex. Saline injection alone increased AChE activity in striatum (68%) and cerebellum (36%) but failed to modify enzyme activity in hippocampus and cerebral cortex. To conclude, AChE sensitivity to convulsant and saline administration is tissue-specific and not restricted to cholinergic areas.
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Affiliation(s)
- E Girardi
- Instituto de Biología Celular, Facultad de Medicina, Universidad de Buenos Aires, Argentina
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Honegger UE, Quack G, Wiesmann UN. Evidence for lysosomotropism of memantine in cultured human cells: cellular kinetics and effects of memantine on phospholipid content and composition, membrane fluidity and beta-adrenergic transmission. PHARMACOLOGY & TOXICOLOGY 1993; 73:202-208. [PMID: 8295847 DOI: 10.1111/j.1600-0773.1993.tb01564.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Memantine, an amantadine derivative, is therapeutically used for the treatment of various neurological and psychiatric disorders such as Parkinson's disease, spasticity, and dementia. Pharmacokinetics of memantine and its effects on phospholipid content and composition, on membrane properties and functions such as fluidity and beta-adrenergic transmission were studied in cultured human fibroblasts and macrophages. The kinetic behaviour of memantine was characteristic for a lysosomotropic drug. Fibroblasts exposed to 14C-memantine in the microM range accumulated the drug up to 200 fold above initial medium concentrations. Lysosomal drug storage was proven by indirect evidence and by analyses of subcellular fractions. Repetitive exposure to memantine resulted in a cumulative uptake. While memantine uptake after single exposure was fully reversible, the rate and extent of release of chronically accumulated drug was reduced but could be enhanced by the addition of unlabelled memantine or ammonium chloride to the medium. Chronic, but not single, exposure to memantine above 10 microM resulted in a concentration dependent phospholipid accumulation and in a shift in the phospholipid composition. There was an overproportionate increase in phosphatidylinositol at the expense of phosphatidylserine and sphingomyelin. Chronic exposure of cultured cells to memantine increased fluidity in the superficial layers of the plasma membrane and reduced the isoproterenol-stimulated cAMP-response without affecting beta-adrenoceptor density. All these findings were compatible with the kinetic behaviour and the effectiveness expected of a weak lysosomotropic drug.
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Affiliation(s)
- U E Honegger
- Department of Pharmacology, University of Bern, Switzerland
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