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Shekh-Ahmad T, Hen N, Yagen B, McDonough JH, Finnell RH, Wlodarczyk BJ, Bialer M. Stereoselective anticonvulsant and pharmacokinetic analysis of valnoctamide, a CNS-active derivative of valproic acid with low teratogenic potential. Epilepsia 2014; 55:353-61. [PMID: 24313671 PMCID: PMC4963464 DOI: 10.1111/epi.12480] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/15/2013] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Valnoctamide (VCD), a central nervous system (CNS)-active chiral constitutional isomer of valpromide, the corresponding amide of valproic acid (VPA), is currently undergoing phase IIb clinical trials in acute mania. VCD exhibits stereoselective pharmacokinetics (PK) in animals and humans. The current study comparatively evaluated the pharmacodynamics (PD; anticonvulsant activity and teratogenicity) and PK of the four individual stereoisomers of VCD. METHODS The anticonvulsant activity of VCD individual stereoisomers was evaluated in several rodent anticonvulsant models including maximal electroshock, 6 Hz psychomotor, subcutaneous metrazol, and the pilocarpine-induced and soman-induced status epilepticus (SE). The PK-PD (anticonvulsant activity) relationship of VCD stereoisomers was evaluated following intraperitoneal administration (70 mg/kg) to rats. Induction of neural tube defects (NTDs) by VCD stereoisomers was evaluated in a mouse strain that was highly susceptible to teratogen-induced NTDs. RESULTS VCD had a stereoselective PK, with (2S,3S)-VCD exhibiting the lowest clearance, and consequently a twice-higher plasma exposure than all other stereoisomers. Nervertheless, there was less stereoselectivity in VCD anticonvulsant activity and each stereoisomer had similar median effective dose (ED)50 values in most models. VCD stereoisomers (258 or 389 mg/kg) did not cause NTDs. These doses are 3-12 times higher than VCD anticonvulsant ED50 values. SIGNIFICANCE VCD displayed stereoselective PK that did not lead to significant stereoselective activity in various anticonvulsant rodent models. If VCD exerted its broad-spectrum anticonvulsant activity using a single mechanism of action (MOA), it is likely that it would exhibit a stereoselective PD. The fact that there was no significant difference between racemic VCD and its individual stereoisomers suggests that VCD's anticonvulsant activity is due to multiple MOAs.
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Affiliation(s)
- Tawfeeq Shekh-Ahmad
- School of Pharmacy, Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Naama Hen
- School of Pharmacy, Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
| | - Boris Yagen
- School of Pharmacy, Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
- David R. Bloom Center for Pharmacy, The Hebrew University of Jerusalem, Israel
| | - John H. McDonough
- Pharmacology Branch, Research Division, US Army Medical Research Institute of Chemical Defense, Maryland, USA
| | - Richard H. Finnell
- Department of Nutritional Sciences, Dell Pediatric Research Institute, The University of Texas at Austin, Austin, Texas, USA
| | - Bogdan J. Wlodarczyk
- Department of Nutritional Sciences, Dell Pediatric Research Institute, The University of Texas at Austin, Austin, Texas, USA
| | - Meir Bialer
- School of Pharmacy, Institute for Drug Research, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem 91120, Israel
- David R. Bloom Center for Pharmacy, The Hebrew University of Jerusalem, Israel
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Myhrer T, Enger S, Mariussen E, Aas P. Two medical therapies very effective shortly after high levels of soman poisoning in rats, but only one with universal utility. Toxicology 2013; 314:221-8. [DOI: 10.1016/j.tox.2013.08.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 08/06/2013] [Accepted: 08/08/2013] [Indexed: 10/26/2022]
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Hen N, Shekh-Ahmad T, Yagen B, McDonough JH, Finnell RH, Wlodarczyk B, Bialer M. Stereoselective pharmacodynamic and pharmacokinetic analysis of sec-Butylpropylacetamide (SPD), a new CNS-active derivative of valproic acid with unique activity against status epilepticus. J Med Chem 2013; 56:6467-77. [PMID: 23879329 DOI: 10.1021/jm4007565] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
sec-Butylpropylacetamide (racemic-SPD) is a chiral CNS-active amide derivative of valproic acid (VPA). This study describes synthesis and stereospecific comparative pharmacodynamics (PD, anticonvulsant activity and teratogenicity) and pharmacokinetic (PK) analysis of four individual SPD stereoisomers. SPD stereoisomers' anticonvulsant activity was comparatively evaluated in several anticonvulsant animal models including the benzodiazepine-resistant status epilepticus (SE). SPD stereoisomers' PK-PD relationship was evaluated in rats. Teratogenicity of SPD stereoisomers was evaluated in SWV mice strain, susceptible to VPA-induced neural tube defect (NTD). SPD stereoisomers (141 or 283 mg/kg) did not cause NTD. SPD has stereoselective PK and PD. (2R,3S)-SPD and (2S,3R)-SPD higher clearance led to a 50% lower plasma exposure that may contribute to their relative lower activity in the pilocarpine-induced SE model. (2S,3S)-SPD, (2R,3R)-SPD, and racemic-SPD have similar anticonvulsant activity and a PK profile that are better than those of (2R,3S)-SPD and (2S,3R)-SPD, making them good candidates for development as new, potent antiepileptics with a potential in benzodiazepine-resistant SE.
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Affiliation(s)
- Naama Hen
- Institute for Drug Research, Faculty of Medicine, School of Pharmacy, The Hebrew University of Jerusalem, Israel
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Garrett TL, Joshi K, Rapp CM, Chapleau M, Cool DR, Schlager JJ, Lucot JB. The effects of 8-OH-DPAT on neuroinflammation after sarin exposure in mice. Toxicology 2013; 310:22-8. [DOI: 10.1016/j.tox.2013.05.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 05/07/2013] [Accepted: 05/10/2013] [Indexed: 10/26/2022]
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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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Dorandeu F, Barbier L, Dhote F, Testylier G, Carpentier P. Ketamine combinations for the field treatment of soman-induced self-sustaining status epilepticus. Review of current data and perspectives. Chem Biol Interact 2013; 203:154-9. [DOI: 10.1016/j.cbi.2012.09.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 09/25/2012] [Accepted: 09/26/2012] [Indexed: 12/21/2022]
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57
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Magnesium sulfate treatment against sarin poisoning: dissociation between overt convulsions and recorded cortical seizure activity. Arch Toxicol 2012; 87:347-60. [DOI: 10.1007/s00204-012-0916-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 07/24/2012] [Indexed: 10/27/2022]
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58
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Determination of anti-convulsant and life-preserving capacities of three types of auto-injector therapies against soman intoxication in rats. Drug Test Anal 2012; 5:693-701. [DOI: 10.1002/dta.1414] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 08/16/2012] [Accepted: 08/17/2012] [Indexed: 11/07/2022]
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de Araujo Furtado M, Rossetti F, Chanda S, Yourick D. Exposure to nerve agents: from status epilepticus to neuroinflammation, brain damage, neurogenesis and epilepsy. Neurotoxicology 2012; 33:1476-1490. [PMID: 23000013 DOI: 10.1016/j.neuro.2012.09.001] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Revised: 07/25/2012] [Accepted: 09/03/2012] [Indexed: 12/17/2022]
Abstract
Epilepsy is a common neurological disorder characterized by an initial injury due to stroke, traumatic brain injury, brain infection, or febrile seizures causing status epilepticus (SE). This phenomenon precedes recurrent (secondary) seizures, the latent period (period without seizures) and downstream appearance of spontaneous recurrent seizures (SRS). Epilepsy inducers include the organophosphorous (OP) compounds modified as chemical warfare nerve agents, such as soman. SE induced by soman is a result of cholinergic system hyperactivity caused by the irreversible inhibition of acetylcholinesterase, and the subsequent increase in the amount of the neurotransmitter acetylcholine at central and peripheral sites. SE leads to profound, permanent, complex and widespread brain damage and associated cognitive and behavioral deficits, accompanied by impaired neurogenesis. Several anticonvulsant and neuroprotective strategies have been studied in order to avoid the epileptogenesis which occurs after SE caused by soman exposure. In recent studies, we showed that SRS occur post-soman exposure and neuropathology can be reduced with diazepam (DZP) and valproic acid (VPA) when administered in combination treatment. These effects are accompanied by neurogenesis seen 15 days post-exposure in the hippocampal dentate gyrus (DG). This review discusses several findings about epilepsy induced by soman exposure such as behavioral changes, EEG anomalies, neuropathology, neuroinflammation, neurogenesis, possible circuitry changes and current strategies for treatment. The soman seizure model is an important model of temporal lobe epilepsy (TLE) and comparable in certain respects with well studied models in the literature such as pilocarpine and kainic acid. All these models together allow for a greater understanding of the different mechanisms of seizure induction, propagation and options for treatment. These studies are very necessary for current military and civilian treatment regimens, against OP nerve agent exposure, which fail to prevent SE resulting in severe neuropathology and epilepsy.
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Affiliation(s)
- Marcio de Araujo Furtado
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Franco Rossetti
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Soma Chanda
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, United States
| | - Debra Yourick
- Center for Military Psychiatry and Neuroscience, Walter Reed Army Institute of Research, Silver Spring, MD, United States.
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Pan H, Hu XZ, Jacobowitz DM, Chen C, McDonough J, Van Shura K, Lyman M, Marini AM. Alpha-linolenic acid is a potent neuroprotective agent against soman-induced neuropathology. Neurotoxicology 2012; 33:1219-29. [PMID: 22884490 DOI: 10.1016/j.neuro.2012.07.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 07/09/2012] [Accepted: 07/09/2012] [Indexed: 11/28/2022]
Abstract
Nerve agents are deadly threats to military and civilian populations around the world. Nerve agents cause toxicity to peripheral and central sites through the irreversible inhibition of acetylcholinesterase, the enzyme that metabolizes acetylcholine. Excessive acetylcholine accumulation in synapses results in status epilepticus in the central nervous system. Prolonged status epilepticus leads to brain damage, neurological dysfunction and poor outcome. Anticonvulsants are effective but must be given rapidly following exposure. Because these agents cause mass casualties, effective neuroprotective agents are needed to reduce brain damage and improve cognitive outcome. α-Linolenic acid is an omega-3 fatty acid that is found in vegetable products and has no known side effects. α-Linolenic acid is neuroprotective against kainic acid-induced brain damage in vivo, but its neuroprotective efficacy against nerve agents is unknown. α-Linolenic acid also exerts anti-depressant and anti-inflammatory activities and enhances synaptic plasticity in vivo. These properties make this polyunsaturated fatty acid (PUFA) a potential candidate against nerve agent-induced neuropathology. Here we show that α-linolenic acid is neuroprotective against soman-induced neuropathology in either a pretreatment or post-treatment paradigm. We also show that subcutaneous injection of α-linolenic acid shows greater neuroprotective efficacy compared with intravenous injection in a brain region-specific manner.
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Affiliation(s)
- Hongna Pan
- Department of Neurology and Program in Neuroscience, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
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61
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Skovira JW, Shih TM, McDonough JH. Neuropharmacological specificity of brain structures involved in soman-induced seizures. Neurotoxicology 2012; 33:463-8. [DOI: 10.1016/j.neuro.2012.03.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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62
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Wang Y, Oguntayo S, Wei Y, Wood E, Brown A, Jensen N, Auta J, Guiodotti A, Doctor BP, Nambiar MP. Neuroprotective effects of imidazenil against chemical warfare nerve agent soman toxicity in guinea pigs. Neurotoxicology 2012; 33:169-77. [DOI: 10.1016/j.neuro.2011.12.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 11/11/2011] [Accepted: 12/29/2011] [Indexed: 01/01/2023]
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63
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Rossetti F, de Araujo Furtado M, Pak T, Bailey K, Shields M, Chanda S, Addis M, Robertson BD, Moffett M, Lumley LA, Yourick DL. Combined diazepam and HDAC inhibitor treatment protects against seizures and neuronal damage caused by soman exposure. Neurotoxicology 2012; 33:500-11. [PMID: 22387230 DOI: 10.1016/j.neuro.2012.02.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 01/23/2012] [Accepted: 02/15/2012] [Indexed: 01/31/2023]
Abstract
The occurrence of status epilepticus (SE) is considered the main cause of brain lesions and morphological alterations, such as hippocampal neuron loss, that result in chronic epilepsy. Previous work demonstrated the convulsive and widespread neuropathological effects of soman, an organophosphorus compound that causes SE and severe recurrent seizures as a result of exposure. Seizures begin rapidly after exposure, can continue for hours, and contribute to prolonged physical incapacitation of the victim. This study attempts to identify anticonvulsive and neuroprotective drugs against soman exposure. Male Sprague-Dawley rats were exposed to 1.0 LD(50) soman. EEGraphical and neuropathological (Fluoro-Jade B staining) effects were analyzed at 72 h post-exposure to soman and subsequent treatments with diazepam (DZP) alone or in combination with histone deacetylase inhibitors, suberoylanilide hydroxamic acid (SAHA) or valproic acid (VPA). The extent of brain damage was dependent on the length of SE and not on the number of recurrent seizures. DZP treatment alone decreased SE time and damage in hippocampus, amygdala, thalamus and cortex, but not in piriform nuclei. The combination of DZP and VPA 100 mg/kg showed more anticonvulsive effects, decreased SE time, and afforded more neuroprotection in the hippocampus, mainly the ventral portion. The combination DZP and SAHA 25 mg/kg was more neuroprotective, but not more anticonvulsant than DZP alone. The DZP combination with VPA HDAC inhibitor proved to be a good treatment for SE and neuronal damage caused by soman exposure.
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Affiliation(s)
- Franco Rossetti
- Walter Reed Army Institute of Research, Silver Spring, MD 20910-7500, United States
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64
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Schultz MK, Wright LKM, Stone MF, Schwartz JE, Kelley NR, Moffett MC, Lee RB, Lumley LA. The anticholinergic and antiglutamatergic drug caramiphen reduces seizure duration in soman-exposed rats: synergism with the benzodiazepine diazepam. Toxicol Appl Pharmacol 2012; 259:376-86. [PMID: 22310180 DOI: 10.1016/j.taap.2012.01.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 01/20/2012] [Accepted: 01/22/2012] [Indexed: 11/26/2022]
Abstract
Therapy of seizure activity following exposure to the nerve agent soman (GD) includes treatment with the anticonvulsant diazepam (DZP), an allosteric modulator of γ-aminobutyric acid A (GABA(A)) receptors. However, seizure activity itself causes the endocytosis of GABA(A) receptors and diminishes the inhibitory effects of GABA, thereby reducing the efficacy of DZP. Treatment with an N-methyl-d-aspartic acid (NMDA) receptor antagonist prevents this reduction in GABAergic inhibition. We examined the efficacy of the NMDA receptor antagonist caramiphen edisylate (CED; 20mg/kg, im) and DZP (10mg/kg, sc), administered both separately and in combination, at 10, 20 or 30min following seizure onset for attenuation of the deleterious effects associated with GD exposure (1.2 LD(50); 132μg/kg, sc) in rats. Outcomes evaluated were seizure duration, neuropathology, acetylcholinesterase (AChE) activity, body weight, and temperature. We also examined the use of the reversible AChE inhibitor physostigmine (PHY; 0.2mg/kg, im) as a therapy for GD exposure. We found that the combination of CED and DZP yielded a synergistic effect, shortening seizure durations and reducing neuropathology compared to DZP alone, when treatment was delayed 20-30min after seizure onset. PHY reduced the number of animals that developed seizures, protected a fraction of AChE from GD inhibition, and attenuated post-exposure body weight and temperature loss independent of CED and/or DZP treatment. We conclude that: 1) CED and DZP treatment offers considerable protection against the effects of GD and 2) PHY is a potential therapeutic option following GD exposure, albeit with a limited window of opportunity.
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Affiliation(s)
- M K Schultz
- US Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010-5400, USA
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Finkelstein A, Kunis G, Berkutzki T, Ronen A, Krivoy A, Yoles E, Last D, Mardor Y, Van Shura K, McFarland E, Capacio BA, Eisner C, Gonzales M, Gregorowicz D, Eisenkraft A, McDonough JH, Schwartz M. Immunomodulation by poly-YE reduces organophosphate-induced brain damage. Brain Behav Immun 2012; 26:159-69. [PMID: 21925261 DOI: 10.1016/j.bbi.2011.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 09/01/2011] [Indexed: 10/17/2022] Open
Abstract
Accidental organophosphate poisoning resulting from environmental or occupational exposure, as well as the deliberate use of nerve agents on the battlefield or by terrorists, remain major threats for multi-casualty events, with no effective therapies yet available. Even transient exposure to organophosphorous compounds may lead to brain damage associated with microglial activation and to long-lasting neurological and psychological deficits. Regulation of the microglial response by adaptive immunity was previously shown to reduce the consequences of acute insult to the central nervous system (CNS). Here, we tested whether an immunization-based treatment that affects the properties of T regulatory cells (Tregs) can reduce brain damage following organophosphate intoxication, as a supplement to the standard antidotal protocol. Rats were intoxicated by acute exposure to the nerve agent soman, or the organophosphate pesticide, paraoxon, and after 24 h were treated with the immunomodulator, poly-YE. A single injection of poly-YE resulted in a significant increase in neuronal survival and tissue preservation. The beneficial effect of poly-YE treatment was associated with specific recruitment of CD4(+) T cells into the brain, reduced microglial activation, and an increase in the levels of brain derived neurotrophic factor (BDNF) in the piriform cortex. These results suggest therapeutic intervention with poly-YE as an immunomodulatory supplementary approach against consequences of organophosphate-induced brain damage.
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Affiliation(s)
- Arseny Finkelstein
- Department of Neurobiology, The Weizmann Institute of Science, Rehovot 76100, Israel
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White HS, Alex AB, Pollock A, Hen N, Shekh-Ahmad T, Wilcox KS, McDonough JH, Stables JP, Kaufmann D, Yagen B, Bialer M. A new derivative of valproic acid amide possesses a broad-spectrum antiseizure profile and unique activity against status epilepticus and organophosphate neuronal damage. Epilepsia 2011; 53:134-46. [PMID: 22150444 DOI: 10.1111/j.1528-1167.2011.03338.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
PURPOSE sec-Butyl-propylacetamide (SPD) is a one-carbon homolog of valnoctamide (VCD), a central nervous system (CNS)-active amide derivative of valproic acid (VPA) currently in phase II clinical trials. The study reported herein evaluated the anticonvulsant activity of SPD in a battery of rodent seizure and epilepsy models and assessed its efficacy in rat and guinea pig models of status epilepticus (SE) and neuroprotection in an organotypic hippocampal slice model of excitotoxic cell death. METHODS The anticonvulsant activity of SPD was evaluated in several rodent seizure and epilepsy models, including maximal electroshock (MES), 6-Hz psychomotor; subcutaneous (s.c.) metrazol-, s.c. picrotoxin, s.c. bicuculline, and audiogenic, corneal, and hippocampal kindled seizures following intraperitoneal administration. Results obtained with SPD are discussed in relationship to those obtained with VPA and VCD. SPD was also evaluated for its ability to block benzodiazepine-resistant SE induced by pilocarpine (rats) and soman (rats and guinea pigs) following intraperitoneal administration. SPD was tested for its ability to block excitotoxic cell death induced by the glutamate agonists N-methyl-D-aspartate (NMDA) and kainic acid (KA) using organotypic hippocampal slices and SE-induced hippocampal cell death using FluoroJade B staining. The cognitive function of SPD-treated rats that were protected against pilocarpine-induced convulsive SE was examined 10-14 days post-SE using the Morris water maze (MWM). The relationship between the pharmacokinetic profile of SPD and its efficacy against soman-induced SE was evaluated in two parallel studies following SPD (60 mg/kg, i.p.) administration in the soman SE rat model. KEY FINDINGS SPD was highly effective and displayed a wide protective index (PI = median neurotoxic dose/median effective dose [TD(50)/ED(50)]) in the standardized seizure and epilepsy models employed. The wide PI values of SPD demonstrate that it is effective at doses well below those that produce behavioral impairment. Unlike VCD, SPD also displayed anticonvulsant activity in the rat pilocarpine model of SE. Thirty minutes after the induction of SE, the calculated rat ED(50) for SPD against convulsive SE in this model was 84 mg/kg. SPD was not neuroprotective in the organotypic hippocampal slice preparation; however, it did display hippocampal neuroprotection in both SE models and cognitive sparing in the MWM, which was associated with its antiseizure effect against pilocarpine-induced SE. When administered 20 and 40 min after SE onset, SPD (100-174 mg/kg) produced long-lasting efficacy (e.g., 4-8 h) against soman-induced convulsive and electrographic SE in both rats and guinea pigs. SPD ED(50) values in guinea pigs were 67 and 92 mg/kg when administered at SE onset or 40 min after SE onset, respectively. Assuming linear pharmacokinetics (PK), the PK-PD (pharmacodynamic) results (rats) suggests that effective SPD plasma levels ranged between 8 and 40 mg/L (20 min after the onset of soman-induced seizures) and 12-50 mg/L (40 min after the onset of soman-induced seizures). The time to peak (t(max)) pharmacodynamic effect (PD-t(max)) occurred after the PK-t(max), suggesting that SPD undergoes slow distribution to extraplasmatic sites, which is likely responsible for antiseizure activity of SPD. SIGNIFICANCE The results demonstrate that SPD is a broad-spectrum antiseizure compound that blocks SE induced by pilocarpine and soman and affords in vivo neuroprotection that is associated with cognitive sparing. Its activity against SE is superior to that of diazepam in terms of rapid onset, potency, and its effect on animal mortality and functional improvement.
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Affiliation(s)
- H Steve White
- Anticonvulsant Drug Development Program, Department of Pharmacology and Toxicology, College of Pharmacy, University of Utah, Salt Lake City, Utah, USA
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Myhrer T, Enger S, Jonassen M, Aas P. Enhanced efficacy of anticonvulsants when combined with levetiracetam in soman-exposed rats. Neurotoxicology 2011; 32:923-30. [DOI: 10.1016/j.neuro.2011.04.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 04/14/2011] [Accepted: 04/25/2011] [Indexed: 10/18/2022]
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Perkins MW, Pierre Z, Rezk P, Song J, Oguntayo S, Morthole V, Sciuto AM, Doctor BP, Nambiar MP. Protective Effects of Aerosolized Scopolamine Against Soman-Induced Acute Respiratory Toxicity in Guinea Pigs. Int J Toxicol 2011; 30:639-49. [DOI: 10.1177/1091581811415874] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The protective efficacy of the antimuscarinic agent scopolamine was evaluated against soman (o-pinacolyl methylphosphonofluoridate [GD])-induced respiratory toxicity in guinea pigs. Anesthetized animals were exposed to GD (841 mg/m3) by microinstillation inhalation exposure and treated 30 seconds later with endotracheally aerosolized scopolamine (0.25 mg/kg) and allowed to recover for 24 hours. Treatment with scopolamine significantly increased survival and reduced clinical signs of toxicity and body weight loss in GD-exposed animals. Analysis of bronchoalveolar lavage (BAL) fluid showed normalization of GD-induced increased cell death, total cell count, and protein following scopolamine treatment. The BAL fluid acetylcholinesterase and butyrylcholinesterase levels were also increased by scopolamine treatment. Respiratory dynamics parameters were normalized at 4 and 24 hours post–GD exposure in scopolamine-treated animals. Lung histology showed that scopolamine treatment reduced bronchial epithelial and subepithelial inflammation and multifocal alveolar septal edema. These results suggest that aerosolized scopolamine considerably protects against GD-induced respiratory toxicity.
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Affiliation(s)
- Michael W. Perkins
- Medical/Analytical Toxicology, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Zdenka Pierre
- Medical/Analytical Toxicology, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Peter Rezk
- Medical/Analytical Toxicology, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Jian Song
- Blast-Induced Neurotrauma Branch, Center for Military Psychiatry and Neurosciences, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Samuel Oguntayo
- Blast-Induced Neurotrauma Branch, Center for Military Psychiatry and Neurosciences, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Venee Morthole
- Department of Pathology, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Alfred M. Sciuto
- Medical/Analytical Toxicology, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD, USA
| | - Bhupendra P. Doctor
- Blast-Induced Neurotrauma Branch, Center for Military Psychiatry and Neurosciences, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Madhusoodana P. Nambiar
- Blast-Induced Neurotrauma Branch, Center for Military Psychiatry and Neurosciences, Walter Reed Army Institute of Research, Silver Spring, MD, USA
- Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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69
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Joosen MJ, van der Schans MJ, van Dijk CG, Kuijpers WC, Wortelboer HM, van Helden HP. Increasing oxime efficacy by blood–brain barrier modulation. Toxicol Lett 2011; 206:67-71. [DOI: 10.1016/j.toxlet.2011.05.231] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Revised: 05/02/2011] [Accepted: 05/03/2011] [Indexed: 01/16/2023]
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70
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O’Donnell JC, McDonough JH, Shih TM. In vivo microdialysis and electroencephalographic activity in freely moving guinea pigs exposed to organophosphorus nerve agents sarin and VX: analysis of acetylcholine and glutamate. Arch Toxicol 2011; 85:1607-16. [DOI: 10.1007/s00204-011-0724-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 06/06/2011] [Indexed: 11/24/2022]
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71
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Che MM, Chanda S, Song J, Doctor BP, Rezk PE, Sabnekar P, Perkins MW, Sciuto AM, Nambiar MP. Aerosolized scopolamine protects against microinstillation inhalation toxicity to sarin in guinea pigs. Toxicol Mech Methods 2011; 21:463-72. [DOI: 10.3109/15376516.2011.562258] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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72
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RamaRao G, Waghmare C, Kumar Gupta A, Bhattacharya BK. Soman-induced alterations of protein kinase C isozymes expression in five discrete areas of the rat brain. Drug Chem Toxicol 2011; 34:221-32. [DOI: 10.3109/01480545.2010.511647] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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73
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Abbara C, Rousseau JM, Lelièvre B, Turcant A, Lallement G, Ferec S, Bardot I, Diquet B. Pharmacokinetic analysis of pralidoxime after its intramuscular injection alone or in combination with atropine-avizafone in healthy volunteers. Br J Pharmacol 2011; 161:1857-67. [PMID: 20804498 DOI: 10.1111/j.1476-5381.2010.01007.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Treatment of organophosphate poisoning with pralidoxime needs to be improved. Here we have studied the pharmacokinetics of pralidoxime after its intramuscular injection alone or in combination with avizafone and atropine using an auto-injector device. EXPERIMENTAL APPROACH The study was conducted in an open, randomized, single-dose, two-way, cross-over design. At each period, each subject received either intramuscular injections of pralidoxime (700 mg), or two injections of the combination: pralidoxime (350 mg), atropine (2 mg), avizafone (20 mg). Pralidoxime concentrations were quantified using a validated LC/MS-MS method. Two approaches were used to analyse these data: (i) a non-compartmental approach; and (ii) a compartmental modelling approach. KEY RESULTS The injection of pralidoxime combination with atropine and avizafone provided a higher pralidoxime maximal concentration than that obtained after the injection of pralidoxime alone (out of bioequivalence range), while pralidoxime AUC values were equivalent. Pralidoxime concentrations reached their maximal value earlier after the injection of the combination. According to Akaike and to goodness of fit criteria, the best model describing the pharmacokinetics of pralidoxime was a two-compartment with a zero-order absorption model. When avizafone and atropine were injected with pralidoxime, the best model describing pralidoxime pharmacokinetics becomes a two-compartment with a first-order absorption model. CONCLUSIONS AND IMPLICATIONS The two approaches, non-compartmental and compartmental, showed that the administration of avizafone and atropine with pralidoxime results in a faster absorption into the general circulation and higher maximal concentrations, compared with the administration of pralidoxime alone.
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Affiliation(s)
- C Abbara
- Université d'Angers, UFR médecine, Angers cedex, F-49045, France.
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74
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The Molecular Toxicology of Chemical Warfare Nerve Agents. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/b978-0-444-53864-2.00003-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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75
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Kadriu B, Guidotti A, Costa E, Davis JM, Auta J. Acute imidazenil treatment after the onset of DFP-induced seizure is more effective and longer lasting than midazolam at preventing seizure activity and brain neuropathology. Toxicol Sci 2010; 120:136-45. [PMID: 21097996 DOI: 10.1093/toxsci/kfq356] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Diazepam (DZ), the preferred anticonvulsant benzodiazepine (BZ) for the treatment of organophosphate (OP) nerve agent-induced seizures and neuronal damage, has been associated with unwanted effects such as sedation, amnesia, cardiorespiratory depression, anticonvulsant tolerance, and dependence liability. In a search for safer and more effective anticonvulsant BZs against OP-induced seizure and neuronal damage, we have previously shown that imidazenil (IMD), a low-intrinsic efficacy positive allosteric modulator of gamma-aminobutyric acid (GABA) action at α1-containing GABA(A) receptors, which has high intrinsic efficacy at α2-, α3-, and α5-containing GABA(A) receptors, is more potent and longer lasting than DZ pretreatment at protecting rats from diisopropyl fluorophosphate (DFP)-induced electrocorticographic (ECoG) seizures and neuronal damage. The effects of IMD were observed at doses that are devoid of sedative, amnestic, and anticonvulsant tolerance actions. In the present study, we compared the anticonvulsant and neuroprotective effects of a combination of atropine (2 mg/kg, ip) and pyridine-2-aldoxime methochloride (2-PAM, 20 mg/kg, ip) with IMD (0.5 mg/kg, ip) or midazolam (MDZ, 0.5-2 mg/kg, ip) administered after the onset of DFP (1.5 mg/kg, sc)-induced seizure activity. The severity of DFP-induced ECoG seizures was assessed by continuous radio telemetry recordings in unrestrained and freely moving rats. Furthermore, the extent of neuronal damage was evaluated using a neuron-specific nuclear protein immunolabeling and fluoro-jade B staining procedure. We report here that IMD is more efficacious and longer lasting than sedating doses of MDZ in protecting rats from DFP-induced ECoG seizures and neuronal damage.
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Affiliation(s)
- Bashkim Kadriu
- Department of Psychiatry, The Psychiatric Institute, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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76
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Deshpande LS, Carter DS, Blair RE, DeLorenzo RJ. Development of a prolonged calcium plateau in hippocampal neurons in rats surviving status epilepticus induced by the organophosphate diisopropylfluorophosphate. Toxicol Sci 2010; 116:623-31. [PMID: 20498005 DOI: 10.1093/toxsci/kfq157] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Organophosphate (OP) compounds are among the most lethal chemical weapons ever developed and are irreversible inhibitors of acetylcholinesterase. Exposure to majority of OP produces status epilepticus (SE) and severe cholinergic symptoms that if left untreated are fatal. Survivors of OP intoxication often suffer from irreversible brain damage and chronic neurological disorders. Although pilocarpine has been used to model SE following OP exposure, there is a need to establish a SE model that uses an OP compound in order to realistically mimic both acute and long-term effects of nerve agent intoxication. Here we describe the development of a rat model of OP-induced SE using diisopropylfluorophosphate (DFP). The mortality, behavioral manifestations, and electroencephalogram (EEG) profile for DFP-induced SE (4 mg/kg, sc) were identical to those reported for nerve agents. However, significantly higher survival rates were achieved with an improved dose regimen of DFP and treatment with pralidoxime chloride (25 mg/kg, im), atropine (2 mg/kg, ip), and diazepam (5 mg/kg, ip) making this model ideal to study chronic effects of OP exposure. Further, DFP treatment produced N-methyl-D-aspartate (NMDA) receptor-mediated significant elevation in hippocampal neuronal [Ca(2+)](i) that lasted for weeks after the initial SE. These results provided direct evidence that DFP-induced SE altered Ca(2+) dynamics that could underlie some of the long-term plasticity changes associated with OP toxicity. This model is ideally suited to test effective countermeasures for OP exposure and study molecular mechanisms underlying neurological disorders following OP intoxication.
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Affiliation(s)
- Laxmikant S Deshpande
- Department of Neurology, Virginia Commonwealth University, Richmond, Virginia 23298, USA
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77
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McDonough JH, McMonagle JD, Shih TM. Time-dependent reduction in the anticonvulsant effectiveness of diazepam against soman-induced seizures in guinea pigs. Drug Chem Toxicol 2010; 33:279-83. [DOI: 10.3109/01480540903483417] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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78
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Changes in mouse brain metabolism following a convulsive dose of soman: A proton HRMAS NMR study. Toxicology 2010; 267:99-111. [DOI: 10.1016/j.tox.2009.10.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Revised: 10/20/2009] [Accepted: 10/21/2009] [Indexed: 11/20/2022]
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79
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Skovira JW, McDonough JH, Shih TM. Protection against sarin-induced seizures in rats by direct brain microinjection of scopolamine, midazolam or MK-801. J Mol Neurosci 2009; 40:56-62. [PMID: 19690985 DOI: 10.1007/s12031-009-9253-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2009] [Accepted: 07/20/2009] [Indexed: 12/29/2022]
Abstract
Control of seizure activity is critical to survival and neuroprotection following nerve agent exposure. Extensive research has shown that three classes of drugs, muscarinic antagonists, benzodiazepines, and N-methyl-D: -aspartate antagonists, are capable of moderating these seizures. This study began to map the neural areas in rat brain that respond to these three drug classes resulting in anticonvulsant effects. Drugs of each class (scopolamine, midazolam, MK-801) were evaluated for their ability to prevent sarin-induced seizures when injected into specific brain areas (lateral ventricle, anterior piriform cortex, basolateral amygdala, area tempestas). Animals were pretreated by microinjection with saline or a dose of drug from one of the three classes 30 min prior to receiving 150 microg/kg sarin, subcutaneously, followed by 2.0 mg/kg atropine methylnitrate, intramuscularly. Animals were then returned to their cages, where electroencephalographic activity was monitored for seizures. Anticonvulsant effective doses (ED(50)) were determined using an up-down dosing procedure over successive animals. Scopolamine provided anticonvulsant effects in each area tested, while midazolam was effective in each area except the lateral ventricle. MK-801 was only effective at preventing seizures when injected into the basolateral amygdala or area tempestas. The results show a unique neuroanatomical and pharmacological specificity for control of nerve agent-induced seizures.
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Affiliation(s)
- Jacob W Skovira
- Pharmacology Branch, Research Division, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5400, USA
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80
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Abbara C, Rousseau JM, Turcant A, Lallement G, Comets E, Bardot I, Clair P, Diquet B. Bioavailability of diazepam after intramuscular injection of its water-soluble prodrug alone or with atropine-pralidoxime in healthy volunteers. Br J Pharmacol 2009; 157:1390-7. [PMID: 19681868 PMCID: PMC2765321 DOI: 10.1111/j.1476-5381.2009.00330.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 03/01/2009] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE The aim of this study was to assess the relative bioavailability of diazepam after administration of diazepam itself or as a water-soluble prodrug, avizafone, in humans. EXPERIMENTAL APPROACH The study was conducted in an open, randomized, single-dose, three-way, cross-over design. Each subject received intramuscular injections of avizafone (20 mg), diazepam (11.3 mg) or avizafone (20 mg) combined with atropine (2 mg) and pralidoxime (350 mg) using a bi-compartmental auto-injector (AIBC). Plasma concentrations of diazepam were quantified using a validated LC/MS-MS assay, and were analysed by both a non-compartmental approach and by compartmental modelling. KEY RESULTS The maximum concentration (C(max)) of diazepam after avizafone injection was higher than that obtained after injection of diazepam itself (231 vs. 148 ng.mL(-1)), while area under the curve (AUC) values were equal. Diazepam concentrations reached their maximal value faster after injection of avizafone. Injection of avizafone with atropine-pralidoxime (AIBC) had no effect on diazepam C(max) and AUC, but the time to C(max) was increased, relative to avizafone injected alone. According to the Akaike criterion, the pharmacokinetics of diazepam after injection as a prodrug was best described as a two-compartment with zero-order absorption model. When atropine and pralidoxime were injected with avizafone, the best pharmacokinetic model was a two-compartment with a first-order absorption model. CONCLUSION AND IMPLICATIONS Diazepam had a faster entry to the general circulation and achieved higher C(max) after injection of prodrug than after the parent drug. Administration of avizafone in combination with atropine and pralidoxime by AIBC had no significant effect on diazepam AUC and C(max).
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Affiliation(s)
- C Abbara
- Université d'Angers, UFR Médecine, Angers Cedex, France.
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81
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Hilmas CJ, Poole MJ, Finneran K, Clark MG, Williams PT. Galantamine is a novel post-exposure therapeutic against lethal VX challenge. Toxicol Appl Pharmacol 2009; 240:166-73. [PMID: 19647007 DOI: 10.1016/j.taap.2009.07.029] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Revised: 07/23/2009] [Accepted: 07/23/2009] [Indexed: 11/29/2022]
Abstract
The ability of galantamine hydrobromide (GAL HBr) treatment to antagonize O-ethyl-S-(2-diisopropylaminoethyl) methylphosphonothiolate (VX)-induced lethality, impairment of muscle tension, and electroencephalographic (EEG) changes was assessed in guinea pigs. Guinea pigs were challenged with 16.8 microg/kg VX (2LD50). One min after challenge, animals were administered 0.5 mg/kg atropine sulfate (ATR) and 25 mg/kg pyridine-2-aldoxime methochloride (2-PAM). In addition, guinea pigs were given 0, 1, 2, 4, 8 or 10 mg/kg GAL as a post-exposure treatment immediately prior to ATR and 2-PAM. Animals were either monitored for 24-h survival, scheduled for electroencephalography (EEG) recording, or euthanized 60 min later for measurement of indirectly-elicited muscle tension in the hemidiaphragm. Post-exposure GAL therapy produced a dose-dependent increase in survival from lethal VX challenge. Optimal clinical benefits were observed in the presence of 10 mg/kg GAL, which led to 100% survival of VX-challenged guinea pigs. Based on muscle physiology studies, GAL post-exposure treatment protected the guinea pig diaphragm, the major effector muscle of respiration, from fatigue, tetanic fade, and muscular paralysis. Protection against the paralyzing effects of VX was dose-dependent. In EEG studies, GAL did not alter seizure onset for all doses tested. At the highest dose tested (10 mg/kg), GAL decreased seizure duration when administered as a post-exposure treatment 1 min after VX. GAL also reduced the high correlation associated between seizure activity and lethality after 2LD50 VX challenge. GAL may have additional benefits both centrally and peripherally that are unrelated to its established mechanism as a reversible acetylcholinesterase inhibitor (AChEI).
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Affiliation(s)
- Corey J Hilmas
- Neurobehavioral Toxicology Branch, Analytical Toxicology Division, U.S. Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Aberdeen Proving Ground, MD 21010, USA.
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82
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Apland JP, Aroniadou-Anderjaska V, Braga MFM. Soman induces ictogenesis in the amygdala and interictal activity in the hippocampus that are blocked by a GluR5 kainate receptor antagonist in vitro. Neuroscience 2008; 159:380-9. [PMID: 19136046 DOI: 10.1016/j.neuroscience.2008.11.053] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2008] [Revised: 11/07/2008] [Accepted: 11/26/2008] [Indexed: 10/21/2022]
Abstract
Exposure to organophosphorus nerve agents induces brain seizures, which can cause profound brain damage resulting in death or long-term cognitive deficits. The amygdala and the hippocampus are two of the most seizure-prone brain structures, but their relative contribution to the generation of seizures after nerve agent exposure is unclear. Here, we report that application of 1 muM soman for 30 min, in rat coronal brain slices containing both the hippocampus and the amygdala, produces prolonged synchronous neuronal discharges (10-40 s duration, 1.5-5 min interval of occurrence) resembling ictal activity in the basolateral nucleus of the amygdala (BLA), but only interictal-like activity ("spikes" of 100-250 ms duration; 2-5 s interval) in the pyramidal cell layer of the CA1 hippocampal area. BLA ictal- and CA1 interictal-like activity were synaptically driven, as they were blocked by the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione. As the expression of the GluR5 subunit of kainate receptors is high in the amygdala, and kainate receptors containing this subunit (GluR5KRs) play an important role in the regulation of neuronal excitability in both the amygdala and the hippocampus, we tested the efficacy of a GluR5KR antagonist against the epileptiform activity induced by soman. The GluR5KR antagonist UBP302 reduced the amplitude of the hippocampal interictal-like spikes, and eliminated the seizure-like discharges in the BLA, or reduced their duration and frequency, with no significant effect on the evoked field potentials. This is the first study reporting in vitro ictal-like activity in response to a nerve agent. Our findings, along with previous literature, suggest that the amygdala may play a more important role than the hippocampus in the generation of seizures following soman exposure, and provide the first evidence that GluR5KR antagonists may be an effective treatment against nerve agent-induced seizures.
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Affiliation(s)
- J P Apland
- Neurotoxicology Branch, USAMRICD, Aberdeen Proving Ground (EA), MD 21010, USA
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83
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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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84
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Park D, Jeon JH, Shin S, Jang JY, Choi BI, Nahm SS, Kang JK, Hwang SY, Kim JC, Kim YB. Debilitating stresses do not increase blood-brain barrier permeability: Lack of the involvement of corticosteroids. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2008; 26:30-37. [PMID: 21783884 DOI: 10.1016/j.etap.2008.01.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2007] [Revised: 12/24/2007] [Accepted: 01/03/2008] [Indexed: 05/31/2023]
Abstract
The involvement of corticosteroids in stress-induced change in blood-brain barrier (BBB) permeability was investigated. Mice were adrenalectomized and administered with pyridostigmine bromide (PB) or Evan's blue, markers of BBB penetration, followed by 18-h cold-restraint stress (CRS). Rats were administered with mifepristone, a corticosteroid receptor blocker, and the markers, followed by 4-h water immersion-restraint stress (WIRS). Separately, soman was administered to induce seizures-mediated BBB opening. CRS did not induce PB and Evan's blue penetration, which were not affected by adrenalectomy. Also, the markers were not detected in the brain of rats subjected to WIRS, regardless of the treatment of mifepristone. In comparison, 1-h epileptic seizures increased the penetration of Evan's blue by 875%. The results suggest that in contrast to seizure-related BBB opening, profound stresses do not practically increase the BBB permeability, and that corticosteroids are not involved in the stress-induced BBB penetration of charged chemicals and albumin-dye complex.
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Affiliation(s)
- Dongsun Park
- College of Veterinary Medicine and Research Institute of Veterinary Medicine, Chungbuk National University, 410 Seongbongro (Gaeshin-dong), Cheongju, Chungbuk 361-763, Republic of Korea
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85
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Reactivation of DFP- and paraoxon-inhibited acetylcholinesterases by pyridinium oximes. Chem Biol Interact 2008; 175:365-7. [PMID: 18565503 DOI: 10.1016/j.cbi.2008.05.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2008] [Revised: 05/08/2008] [Accepted: 05/09/2008] [Indexed: 11/20/2022]
Abstract
Exposure to the organophosphorus nerve agents such as sarin, soman, cyclosarin, and VX causes acute intoxication by inhibiting acetylcholinesterase (AChE), where the serine residue of the active site can attack the phosphorous atom of the organophosphorus agents to form a strong P-O bond. The purpose of the present study was to evaluate new oxime antidotes to reactivate the inhibited AChE. We have designed and synthesized several new oximes, and have evaluated the substances that differ from the currently used oximes in linker between the two pyridinium rings. The potency of newly synthesized oximes was compared with two currently used AChE reactivators (2-PAM, HI-6). The reactivation potencies of the bis-pyridinium oximes connected with a (CH(2))(n) linker between the two quaternary nitrogen atoms were evaluated with housefly (HF) AChE inhibited by diisopropyl fluorophosphates (DFP) and by paraoxon. The bis-pyridinium oximes showed stronger activity compared with mono-pyridinium oxime, and the magnitude of reactivation potency depended on the length of the methylene linker. The potency order was (CH(2))<(CH(2))(2)<(CH(2))(3)>(CH(2))(4)>(CH(2))(7). A (CH(2))(3) linker was optimal in HF AChE inhibited by either DFP or paraoxon. Thus, bis-pyridinium oxime 5 which has (CH(2))(3) linker showed the highest activity in this series of compounds. Interestingly, 5 was not as active as 2-PAM, showing that the position of the oxime group on the pyridinium ring is also very important for the reactivation potency.
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86
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Johnson EA, Daugherty KS, Gallagher SJ, Moran AV, DeFord SM. Glutamate receptor pathology is present in the hippocampus following repeated sub-lethal soman exposure in the absence of spatial memory deficits. Neurotoxicology 2007; 29:73-80. [PMID: 17942156 DOI: 10.1016/j.neuro.2007.09.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 09/05/2007] [Accepted: 09/06/2007] [Indexed: 11/25/2022]
Abstract
Much is still unknown about the long-term effects of repeated, sub-lethal exposure to organophosphorus (OP) nerve agents, such as soman (GD), on learning and memory tasks and related protein expression in the hippocampus. In the present study, guinea pigs were exposed to sub-lethal doses of GD for 10 days and cognitive performance assessed using the Morris water maze (MWM) up to 88 days post-exposure to investigate spatial learning. Additionally, hippocampal lysates were probed for cytoskeletal, synaptic and glutamate receptor proteins using Western blot analyses. No significant difference in MWM performance was observed between repeated sub-lethal GD exposed and saline control groups. However, Western blot analyses revealed significant changes in glutamate receptor protein immunoreactivity for subunits GluR2, NMDAR1, NMDAR2a and NMDAR2b in the hippocampi of GD-exposed guinea pigs. Levels of GluR2, NMDAR2a and NMDAR2b increased by 3 months post-initial exposure and returned to control levels by 6 months while NMDAR1 decreased by 6 months. No significant differences in neurofilament medium (NFM), neurofilament light (NFL) or synaptophysin densitometry were detected and alpha-II-spectrin proteolytic breakdown was also absent. These results reveal that repeated, sub-lethal exposure to GD affects glutamate receptor subunit expression but does not affect cytoskeletal protein immunoreactivity or the proteolytic state in the hippocampus. Though these changes do not affect spatial memory, they may contribute to other cognitive deficits previously observed following sub-lethal OP exposure.
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Affiliation(s)
- Erik A Johnson
- US Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Road, Comparative Medicine Division, Comparative Pathology Branch, Aberdeen Proving Ground, MD 21010-5400, USA.
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87
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Myhrer T. Neuronal structures involved in the induction and propagation of seizures caused by nerve agents: Implications for medical treatment. Toxicology 2007; 239:1-14. [PMID: 17689166 DOI: 10.1016/j.tox.2007.06.099] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Revised: 06/15/2007] [Accepted: 06/18/2007] [Indexed: 11/30/2022]
Abstract
In epilepsy research, studies have been made to identify brain areas critical for triggering and/or controlling propagated seizure activity. The purpose of the present study was to focus on a similar approach in nerve agent research by reviewing relevant literature to map potential trigger sites and propagation pathways for seizures. The piriform cortex and medial septal area emerge as prime target areas for soman-induced seizures. The cholinergic hyperactivation in the latter structures seems to induce increased glutamatergic activity in the piriform, entorhinal, and perirhinal cortices along with the hippocampal region. For prophylactic or early treatment, mapping of muscarinic subreceptors in the piriform cortex and medial septum would be guiding for designing anticholinergic drugs with optimal properties. Sustained seizures governed by glutamatergic over-activity may primarily be terminated by drugs with optimal glutamatergic antagonism primarily in the piriform, entorhinal, and perirhinal cortices. Studies of radiolabeled ligands to map subreceptors may provide specification of wanted drug properties to guide the choice among existing agents or to synthesize novel ones.
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Affiliation(s)
- Trond Myhrer
- Norwegian Defence Research Establishment, Protection Division, NO-2027, Kjeller, Norway.
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88
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Myhrer T, Enger S, Aas P. Anticonvulsant efficacy of drugs with cholinergic and/or glutamatergic antagonism microinfused into area tempestas of rats exposed to soman. Neurochem Res 2007; 33:348-54. [PMID: 17710542 DOI: 10.1007/s11064-007-9429-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2007] [Accepted: 06/29/2007] [Indexed: 10/22/2022]
Abstract
A group of antiparkinson drugs (benactyzine, biperiden, caramiphen, procyclidine, and trihexyphenidyl) has been shown to possess both anticholinergic and antiglutamatergic properties, making these agents very well suited as anticonvulsants against nerve agents. The first purpose of this study was to make a comparative assessment of the anticonvulsant potencies of the antiparkinson agents when microinfused (1 microl) into the seizure controlling area tempestas (AT) of rats 20 min before subcutaneous injection of soman (100 microg/kg). The second purpose was to determine whether cholinergic and/or glutamatergic antagonism was the effective property. The results showed that only procyclidine (6 microg) and caramiphen (10 microg) antagonized soman-induced seizures. Cholinergic, and not glutamatergic, antagonism was likely the active property, since atropine (100 microg), and scopolamine (1 microg) caused anticonvulsant effects, whereas MK-801 (1 microg), and ketamine (50 microg) did not. Soman (11 nmol) injected into AT resulted more frequently in clonic convulsions than full tonic-clonic convulsions. AT may serve as both a trigger site for soman-evoked seizures and a site for screening anticonvulsant potencies of future countermeasures.
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Affiliation(s)
- Trond Myhrer
- Norwegian Defence Research Establishment, Protection Division, P.O. Box 25, 2027 Kjeller, Norway.
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89
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Haug KH, Myhrer T, Fonnum F. The combination of donepezil and procyclidine protects against soman-induced seizures in rats. Toxicol Appl Pharmacol 2007; 220:156-63. [PMID: 17289099 DOI: 10.1016/j.taap.2006.12.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2006] [Revised: 12/21/2006] [Accepted: 12/22/2006] [Indexed: 01/17/2023]
Abstract
Current treatment of nerve agent poisoning consists of prophylactic administration of pyridostigmine and therapy using atropine, an oxime and a benzodiazepine. Pyridostigmine does however not readily penetrate the blood-brain barrier giving ineffective protection of the brain against centrally mediated seizure activity. In this study, we have evaluated donepezil hydrochloride, a partial reversible inhibitor of acetylcholinesterase (AChE) clinically used for treating Alzheimer's disease, in combination with procyclidine, used in treatment of Parkinson's disease and schizophrenia, as prophylaxis against intoxication by the nerve agent soman. The results demonstrated significant protective efficacy of donepezil (2.5 mg/kg) combined with procyclidine (3 or 6 mg/kg) when given prophylactically against a lethal dose of soman (1.6 x LD(50)) in Wistar rats. No neuropathological changes were found in rats treated with this combination 48 h after soman intoxication. Six hours after soman exposure cerebral AChE activity and acetylcholine (ACh) concentration was 5% and 188% of control, respectively. The ACh concentration had returned to basal levels 24 h after soman intoxication, while AChE activity had recovered to 20% of control. Loss of functioning muscarinic ACh receptors (17%) but not nicotinic receptors was evident at this time point. The recovery in brain AChE activity seen in our study may be due to the reversible binding of donepezil to the enzyme. Donepezil is well tolerated in humans, and a combination of donepezil and procyclidine may prove useful as an alternative to the currently used prophylaxis against nerve agent intoxication.
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Affiliation(s)
- Kristin Huse Haug
- Department of Biochemistry, Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1112, N-0317 Oslo, Norway.
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90
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Radić B, Vrdoljak AL, Petek MJ, Kopjar N, Zeljezić D. In vitro biological efficiency of tenocyclidine – TCP and its adamantane derivative TAMORF. Toxicol In Vitro 2006; 20:1455-64. [PMID: 16942853 DOI: 10.1016/j.tiv.2006.07.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 06/01/2006] [Accepted: 07/05/2006] [Indexed: 11/19/2022]
Abstract
Tenocyclidine-TCP showing a broad spectrum of pharmacological activity including antidotal effect in organophosphorus compounds poisoning, radioprotective and anticancer effects. We investigated in vitro interactions of TCP and its adamantane derivative--TAMORF with human erythrocyte acetylcholinesterase (AChE). Moreover, their genotoxicity and radioprotective activity on human white blood cells were studied using the alkaline comet assay, viability testing and the analysis of the structural chromosome aberrations. The tested compounds were found to be weak inhibitors of AChE, for TCP IC(50)=1 x 10(-5)M and for TAMORF IC(50)>1 x 10(-3)M, without reactivating and protective effects on AChE inhibited by soman. Results suggest that TCP modified by the replacement of the cyclohexyl ring with an adamantly ring and piperidine with morpholine group (TAMORF) have lower toxicity. Both compounds possess low cytotoxicity and radioprotective activity, but TAMORF also shows cell growth inhibitory effects. To clarify differences in their biological efficiency observed in vitro and in vivo, additional analyses are necessary. Since TAMORF was found to significantly inhibit cell growth and proliferation in vitro, it is reasonably to consider it as a source molecule promising for further modifications and development of more potent substances with antitumor properties rather then radioprotector or antidote in organophosphorus poisoning.
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Affiliation(s)
- Bozica Radić
- Institute for Medical Research and Occupational Health, Ksaverska c. 2, HR-10 000 Zagreb, Croatia
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91
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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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92
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Shih TM, Rowland TC, McDonough JH. Anticonvulsants for nerve agent-induced seizures: The influence of the therapeutic dose of atropine. J Pharmacol Exp Ther 2006; 320:154-61. [PMID: 17015638 DOI: 10.1124/jpet.106.111252] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Two guinea pig models were used to study the anticonvulsant potency of diazepam, midazolam, and scopolamine against seizures induced by the nerve agents tabun, sarin, soman, cyclosarin, O-ethyl S-(2-(diisopropylamino)ethyl)methylphosphonothioate (VX), and O-isobutyl S-(2-diethylamino)ethyl)-methyl phosphonothioate (VR). Animals instrumented for electroencephalogram recording were pretreated with pyridostigmine bromide (0.026 mg/kg i.m.) 30 min before challenge with 2 x LD50 (s.c.) of a nerve agent. In model A, atropine sulfate (2.0 mg/kg i.m.) and pyridine-2-aldoxime methylchloride (2-PAM; 25.0 mg/kg i.m.) were given 1 min after nerve agent challenge, and the tested anticonvulsant was given (i.m.) 5 min after seizure onset. In model B, a lower dose of atropine sulfate (0.1 mg/kg i.m.) was given along with 2-PAM 1 min after nerve agent challenge, and the anticonvulsant was given at seizure onset. With the lower dose of atropine, seizure occurrence increased to virtually 100% for all agents; the time to seizure onset decreased for sarin, cyclosarin, and VX; the signs of nerve agent intoxication were more severe; and coma resulted frequently with cyclosarin. The anticonvulsant ED50 doses for scopolamine or diazepam were, in general, not different between the two models, whereas the anticonvulsant ED50 values of midazolam increased 3- to 17-fold with the lower atropine dose. Seizure termination times were not systematically effected by the different doses of atropine. The order of anticonvulsant effectiveness within each model was scopolamine > or = midazolam > diazepam. The findings indicate that the dose of atropine given as antidotal therapy can significantly influence measures of nerve agent toxicity and responsiveness to anticonvulsant therapy.
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Affiliation(s)
- Tsung-Ming Shih
- Pharmacology Branch, Research Division, United States Army Medical Research Institute of Chemical Defense, 3100 Ricketts Point Rd., Aberdeen Proving Ground, MD 21010-5400, USA.
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93
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Myhrer T, Enger S, Aas P. Pharmacological therapies against soman-induced seizures in rats 30 min following onset and anticonvulsant impact. Eur J Pharmacol 2006; 548:83-9. [PMID: 16949571 DOI: 10.1016/j.ejphar.2006.07.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2006] [Revised: 06/19/2006] [Accepted: 07/04/2006] [Indexed: 10/24/2022]
Abstract
Systemic administration does not allow a clear differentiation between the anticonvulsant properties of GABAA (gamma-aminobutyric acid) modulators. For this reason, various GABAA modulators have previously been micro-infused into seizure controlling substrates (area tempestas, substantia nigra) in the rat brain as a screening method for potential systemic administration. The purpose of the present study was to examine the anticonvulsant impact of the GABAergic modulators muscimol, ethanol, and propofol (screened by micro-infusions) when each drug was combined with procyclidine and administered systemically. The results showed that all 3 combinations could effectively terminate soman-induced (100 microg/kg s.c.) seizures when administered 30-35 min after onset. Procyclidine and propofol were considered as the most relevant double regimen to replace a previous triple regimen (procyclidine, diazepam, pentobarbital) against soman-induced seizures. Additionally, it was shown that unilateral implantation of hippocampal electrodes resulted in increased resistance to aphagia/adipsia and neuropathology, but not to lethality following soman. Efficient pharmacological treatment of soman-induced seizures at an early stage (< 20 min) is crucial to avoid neuropathology and cognitive deficits.
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Affiliation(s)
- Trond Myhrer
- Norwegian Defence Research Establishment, Protection Division, NO-2027 Kjeller, Norway.
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94
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Dorandeu F, Mikler JR, Thiermann H, Tenn C, Davidson C, Sawyer TW, Lallement G, Worek F. Swine models in the design of more effective medical countermeasures against organophosphorus poisoning. Toxicology 2006; 233:128-44. [PMID: 17092624 DOI: 10.1016/j.tox.2006.09.013] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 09/15/2006] [Accepted: 09/25/2006] [Indexed: 11/16/2022]
Abstract
Although the three most commonly used large mammal species in the safety assessment of drugs remain the dog, the macaque and the marmoset, swine, especially minipigs, have also been widely used over the years in many toxicological studies. Swine present a number of interesting biological and physiological characteristics. Similarities in skin properties with humans have led to extensive in vitro and in vivo studies. There is a specific interest in cardiovascular research, as well as in anaesthesiology and critical care medicine due to common features of swine and human physiology. Although knowledge of swine brain structure and functions remains incomplete, data does exist. The multiple blood sampling that is necessary in pharmacokinetic and toxicokinetic studies are possible, as well as multiparametric monitoring and interventions with equipment used in human clinical settings. Practicality (handling), scientific (stress reduction) and ethical (invasive monitoring) reasons have led research teams to incorporate anaesthesia into their paradigms which makes the analysis of data increasingly difficult. Although not substantiated by scientific data, the swine appears to have an intermediate position in the scale of public perception between non-human primates and animals commonly referred to as pets (i.e. dogs and cats) and rodents. The benefits of the swine model justify the use of these animals in the design of more effective medical countermeasures against known chemical warfare agents (nerve agents, vesicants and lung damaging agents). Exposure to organophosphorus (OP) pesticides represents a severe health issue in developing countries, while OP intoxication with the more lethal military nerve agents is not only of military concern but also a terrorist threat. Tailoring therapeutic regimens to the reality of OP poisoning is of the utmost importance when little experimental data and sparse human clinical data are available in the decision making process. We will present some of the advantages and disadvantages of the swine model in OP countermeasures elaborating on two examples. First, we will present the issues related to the use of anaesthesia during experimental OP poisoning and second we will show how results from experiments with swine can be integrated into a kinetic-based dynamic model to evaluate oxime efficacy. A better knowledge of OP poisoning in swine (comparative toxicokinetics, pharmacokinetics and biochemistry) is definitely necessary before accepting it as a first choice non-rodent model. However, there exists a large amount of data in the model on anaesthesia and different types of shock favouring their use for evaluation of complex situations such as the anaesthesia of OP poisoned patients and combined injuries.
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Affiliation(s)
- F Dorandeu
- Département de Toxicologie, Centre de Recherches du Service de Santé des Armées, 24 Avenue des Maquis du Gresivaudan, BP 87, F-38702 La Tronche Cedex, France.
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95
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Myhrer T, Enger S, Aas P. Efficacy of immediate and subsequent therapies against soman-induced seizures and lethality in rats. Basic Clin Pharmacol Toxicol 2006; 98:184-91. [PMID: 16445593 DOI: 10.1111/j.1742-7843.2006.pto_268.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The purpose of the present study was to examine the efficacy of a triple combination of drugs with adequate anticonvulsant effects and a dual combination with inadequate anticonvulsant effects followed by adjunct therapy. The results showed that combined intramuscular injections of HI-6 (42 mg/kg), atropine (14 mg/kg), and avizafone (3 mg/kg) administered 1, 16, and 31 min. after exposure to a soman dose of 4 x LD(50) completely terminated seizures with a moderate mortality rate (25%). When the soman dose was lowered to 3 x LD(50) the anticonvulsant effect was complete, and no rats died within 24 hr. Rats challenged with 5 x LD(50) of soman all died within 10 min. Without avizafone in the combination, seizures induced by 3 or 4 x LD(50) of soman could not be terminated unless an adjunct therapy consisting of procyclidine (6 mg/kg), diazepam (10 mg/kg), and pentobarbital (30 kg/kg) was given, and the mortality rate was comparatively high (78%). Administration of the adjunct therapy alone 6-16 min. after 4 x LD(50) of soman stopped the seizure activity, but all the rats died within 24 hr. Marked neuropathology was found in the piriform cortex and amygdala, whereas the hippocampal CA1 field was effectively protected when both the triple combination and the dual combination plus adjuncts had stopped seizures 35-55 min. after onset. It is concluded that termination of soman-induced seizures at an early stage (<20 min.) is crucial to avoid neuronal pathology.
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Affiliation(s)
- Trond Myhrer
- Norwegian Defence Research Establishment, Protection Division, P.O. Box 25, NO-2027 Kjeller, Norway.
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96
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Chapman S, Kadar T, Gilat E. Seizure duration following sarin exposure affects neuro-inflammatory markers in the rat brain. Neurotoxicology 2006; 27:277-83. [PMID: 16406030 DOI: 10.1016/j.neuro.2005.11.009] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 11/20/2005] [Accepted: 11/20/2005] [Indexed: 10/25/2022]
Abstract
The current study was aimed to characterize for the first time the alterations in the characteristic neuro-inflammatory markers triggered by sarin exposure in the rat's brain, and to investigate its dependency on seizure duration. Centrally mediated seizures are a common consequence of exposure to organophosphates (OP) despite conventional treatment with atropine and an oxime. In the present study midazolam, was used to control duration and intensity of seizures. The levels of the pro-inflammatory cytokine peptides IL-1beta, IL-6, TNF-alpha and prostaglandin E2 (PGE2) were monitored at various times after sarin exposure in the hippocampus and cortex of rats treated with midazolam following 5 or 30 min of seizure activity. Biochemical evaluation of brain tissues revealed a significant increase in the level of the pro-inflammatory peptides starting at 2 h and peaking at 2-24 h following sarin. Hippocampal values of IL1-beta increased from 1.2+/-0.1 pg/mg tissue (control), to 2.4+/-0.3 at 2 h (5 min seizure) and to 9.3+/-2.5 at 8h (30 min seizure). PGE2 level in the hippocampus increased up to 24 h following exposure (from 56+/-3 to 175+/-26 and 277+/-28 pg/mg tissue) following 5 and 30 min of seizure activity respectively. Thus, unlike limitation of seizures to 5 min by midazolam, delayed treatment (30 min) resulted in prolonged seizures and pronounced increase in cytokines and PGE2. In addition, a second increase in inflammatory markers was observed 30 days following sarin exposure only in rats treated following 30 min of seizure activity. Histological evaluation of the rat brain, conducted in this study, revealed lack of damage in the hippocampus and piriform cortex with minor lateral ventricles enlargement in few animals following 5 min of sarin-induced seizure activity. In contrast, marked histological damage to the brain was demonstrated following 30 min of seizure activity, consisting severe damage to the hippocampus, piriform cortex and some thalamic nuclei. In summary, a novel characterization of the prolonged central neuro-inflammatory process that accompanies sarin exposure is presented. The timing of the anticonvulsive treatment was shown to be crucial in modulation of the neuro-inflammatory response, and may implicate the consequent long-term brain damage.
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Affiliation(s)
- S Chapman
- Department of Pharmacology, Israel Institute for Biological Research, P.O. Box 19, Ness Ziona 74100, Israel
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97
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Bhagat YA, Obenaus A, Hamilton MG, Mikler J, Kendall EJ. Neuroprotection From Soman-induced Seizures In The Rodent: Evaluation With Diffusion- And T2-weighted Magnetic Resonance Imaging. Neurotoxicology 2005; 26:1001-13. [PMID: 15982742 DOI: 10.1016/j.neuro.2005.04.006] [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: 12/09/2004] [Accepted: 04/13/2005] [Indexed: 11/20/2022]
Abstract
Exposure to the organophosphate nerve agent soman produces seizures that in turn lead to neuropathology. This study describes the temporal and spatial evolution of brain pathology following soman-induced convulsions and the attenuation of these alterations after neuroprotective intervention with magnetic resonance imaging (MRI). Neuroimaging 12 h after soman exposure, the hippocampus and thalamus exhibited significant decreases (23%) in apparent diffusion coefficients (ADC). These acute effects were resolved by 7 days. In addition, T2 measurements declined significantly at 12 h (37%) returning to near normal values by 24 h. Histopathological analyses confirmed moderate cell loss within the hippocampus and piriform cortex. Together these findings suggest that initial cell death was resolved through regional cellular remodeling. Pharmacological countermeasures were administered in the form of diazepam, a benzodiazepine anticonvulsant, or gacyclidine (GK-11), an anti-glutamatergic compound. Diazepam therapy applied immediately after soman exposure prevented acute ADC changes. However the presence of edema, using T2 measurements, was detected at 3 h within the retrosplenial, amygdala and piriform cortices and at 12 h in the thalamus (34% below normal). GK-11 therapy appeared to prevent most of these changes. However at 7 days after soman, a decrease (17%) in ADC was observed in the piriform cortex. Pathology was confined to the piriform cortex suggesting that this region is more difficult to protect. This is the first report that provides temporal and spatial resolution using MRI with histological correlation of pharmacological interventions against soman-mediated seizure-induced neuropathology.
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Affiliation(s)
- Yusuf A Bhagat
- Department of Medical Imaging, College of Medicine, Royal University Hospital, University of Saskatchewan, 103 Hospital Drive, Saskatoon, Sask., Canada
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98
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Dorandeu F, Carpentier P, Baubichon D, Four E, Bernabé D, Burckhart MF, Lallement G. Efficacy of the ketamine-atropine combination in the delayed treatment of soman-induced status epilepticus. Brain Res 2005; 1051:164-75. [PMID: 16005443 DOI: 10.1016/j.brainres.2005.06.013] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2005] [Revised: 06/03/2005] [Accepted: 06/07/2005] [Indexed: 10/25/2022]
Abstract
Nerve agent poisoning is known to induce full-blown seizures, seizure-related brain damage (SRBD), and lethality. Effective and quick management of these seizures is critical. In conditions of delayed treatment, presently available measures are inadequate calling for optimization of therapeutic approaches. The effects of ketamine/atropine sulfate (KET/AS) combinations were thus assessed as potential valuable delayed therapy in soman-poisoned male guinea pigs. Animals received pyridostigmine (26 microg/kg, i.m.) 30 min before soman (62 microg/kg, i.m.) followed by therapy consisting of atropine methyl nitrate (4 mg/kg) 1 min later. KET was then administered i.m. at different times after the onset of seizures, starting at 30 min post-poisoning. KET was always injected with atropine sulfate, itself given at a dose that was unable to modify seizures (2 to 10 mg/kg). Different treatment schemes (dose and time of injection) were evaluated. Sub-anesthetic doses of KET (10 mg/kg) could prevent lethality and stop ongoing seizures only when administered 30 min after challenge. An extended delay before treatment (up to 2 h) called for an increase in KET dose (up to 60 mg/kg three times), thus reaching anesthetic levels but without the need of any ventilation support. KET proved effective in stopping seizures, highly reducing SRBD and allowing survival with a progressive loss of efficacy when treatment was delayed beyond 1 h post-challenge. Preliminary results suggest that association with the benzodiazepine midazolam (1 mg/kg) might be interesting when treatment is initiated 2 h after poisoning, i.e., when KET efficacy is dramatically reduced. All in all, these observations suggest that KET, in association with atropine sulfate and possibly other drugs, may be highly effective in the delayed treatment of severe soman intoxication.
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Affiliation(s)
- Frederic Dorandeu
- Département de Toxicologie, CRSSA, 24 avenue des Maquis du Gresivaudan, F-38 702 La Tronche, France.
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99
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Gilat E, Kadar T, Levy A, Rabinovitz I, Cohen G, Kapon Y, Sahar R, Brandeis R. Anticonvulsant treatment of sarin-induced seizures with nasal midazolam: An electrographic, behavioral, and histological study in freely moving rats. Toxicol Appl Pharmacol 2005; 209:74-85. [PMID: 16271623 DOI: 10.1016/j.taap.2005.03.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 03/07/2005] [Accepted: 03/16/2005] [Indexed: 10/25/2022]
Abstract
Centrally mediated seizures and convulsions are common consequences of exposure to organophosphates (OPs). These seizures rapidly progress to status epilepticus (SE) and contribute to profound brain injury. Effective management of these seizures is critical for minimization of brain damage. Nasal application of midazolam (1.5 mg/kg) after 5 min of sarin-induced electrographic seizure activity (EGSA) ameliorated EGSA and convulsive behavior (238 +/- 90 s). Identical treatment after 30 min was not sufficient to ameliorate ECoG paradoxical activity and convulsive behavior. Nasal midazolam (1.5 mg/kg), together with scopolamine (1 mg/kg, im) after 5 min of EGSA, exerted a powerful and rapid anticonvulsant effect (53 +/- 10 s). Delaying the same treatment to 30 min of EGSA leads to attenuation of paroxysmal ECoG activity in all cases but total cessation of paroxysmal activity was not observed in most animals tested. Cognitive tests utilizing the Morris Water Maze demonstrated that nasal midazolam alone or together with scopolamine (im), administered after 5 min of convulsions, abolished the effect of sarin on learning. Both these treatments, when given after 30 min of convulsions, only decreased the sarin-induced learning impairments. Whereas rats which were not subject to the anticonvulsant agents did not show any memory for the platform location, both treatments (at 5 min as well as at 30 min) completely abolished the memory deficits. Both treatments equally blocked the impairment of reversal learning when given at 5 min. However, when administered after 30 min, midazolam alone reversed the impairments in reversal learning, while midazolam with scopolamine did not. Rats exposed to sarin and treated with the therapeutic regimen with the exclusion of midazolam exhibited severe brain lesions that encountered the hippocampus, pyriform cortex, and thalamus. Nasal midazolam at 5 min prevented brain damage, while delaying the midazolam treatment to 30 min of EGSA resulted in brain damage. The addition of scopolamine to midazolam did not alter the above observation. In summary, nasal midazolam treatment briefly after initiation of OP-induced seizure leads to cessation of EGSA and prevented brain lesions and behavioral deficiencies in the rat model.
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Affiliation(s)
- E Gilat
- Department of Pharmacology, Israel Institute for Biological Research, Ness Ziona, 74100 Israel.
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Kim WS, Cho Y, Kim JC, Huang ZZ, Park SH, Choi EK, Shin S, Nam SY, Kang JK, Hwang SY, Kim YB. Protection by a transdermal patch containing physostigmine and procyclidine of soman poisoning in dogs. Eur J Pharmacol 2005; 525:135-42. [PMID: 16256978 DOI: 10.1016/j.ejphar.2005.09.052] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Revised: 09/18/2005] [Accepted: 09/27/2005] [Indexed: 10/25/2022]
Abstract
The prophylactic efficacy of a combinational patch system containing physostigmine and procyclidine against soman intoxication was evaluated using dogs. Female beagle dogs (body weights 9-10 kg) were shaved on the abdominal side, attached with a matrix-type patch (7x7 cm) containing 1.5% of physostigmine plus 6% procyclidine for 2 days, and challenged with subcutaneous injection of serial doses (2-10 LD50) of soman. Separately, in combination with the patch attachment, atropine (2 mg/dog) plus 2-pralidoxime (600 mg/dog) or atropine plus 1-[([4-(aminocarbonyl)pyridinio]methoxy)methyl]-2-[(hydroxyimino)methyl]pyridinium (HI-6, 500 mg/dog) were injected intramuscularly 1 min after soman poisoning. The LD50 value of soman was determined to be 9.1 microg/kg, and high doses (> or = 1.4 LD50) of soman induced salivation, emesis, defecation and diarrhea, tremors and seizures, and recumbency of dogs, leading to 100% mortality in 24 h. The prophylactic patch, which led to mean 18.5-18.8% inhibition of blood cholinesterase activity by physostigmine and mean 7.9-8.3 ng/ml of blood concentration of procyclidine, exerted a high protection ratio (4.7 LD50), in comparison with relatively-low effects of traditional antidotes, atropine plus 2-pralidoxime (2.5 LD50) and atropine plus HI-6 (2.7 LD50). Noteworthy, a synergistic increase in the protection ratio was achieved by the combination of the patch with atropine plus HI-6 (9 LD50), but not with atropine plus 2-pralidoxime (5 LD50). In addition, the patch system markedly attenuated the cholinergic signs and seizures induced by soman, especially when combined with atropine plus HI-6, leading to elimination of brain injuries and physical incapacitation up to 6 LD50 of soman poisoning. Taken together, it is suggested that the patch system containing physostigmine and procyclidine, especially in combination with atropine and HI-6, could be a choice for the quality survival from nerve-agent poisoning.
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Affiliation(s)
- Wang-Soo Kim
- Biomedical Section, Agency for Defense Development, Yuseong P.O. Box 35-1, Daejeon 305-600, Republic of Korea
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