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Charkhkar H, Meyyappan S, Matveeva E, Moll JR, McHail DG, Peixoto N, Cliff RO, Pancrazio JJ. Amyloid beta modulation of neuronal network activity in vitro. Brain Res 2015; 1629:1-9. [PMID: 26453830 DOI: 10.1016/j.brainres.2015.09.036] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 09/17/2015] [Accepted: 09/29/2015] [Indexed: 01/10/2023]
Abstract
In vitro assays offer a means of screening potential therapeutics and accelerating the drug development process. Here, we utilized neuronal cultures on planar microelectrode arrays (MEA) as a functional assay to assess the neurotoxicity of amyloid-β 1-42 (Aβ42), a biomolecule implicated in the Alzheimer׳s disease (AD). In this approach, neurons harvested from embryonic mice were seeded on the substrate-integrated microelectrode arrays. The cultured neurons form a spontaneously active network, and the spiking activity as a functional endpoint could be detected via the MEA. Aβ42 oligomer, but not monomer, significantly reduced network spike rate. In addition, we demonstrated that the ionotropic glutamate receptors, NMDA and AMPA/kainate, play a role in the effects of Aβ42 on neuronal activity in vitro. To examine the utility of the MEA-based assay for AD drug discovery, we tested two model therapeutics for AD, methylene blue (MB) and memantine. Our results show an almost full recovery in the activity within 24h after administration of Aβ42 in the cultures pre-treated with either MB or memantine. Our findings suggest that cultured neuronal networks may be a useful platform in screening potential therapeutics for Aβ induced changes in neurological function.
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Affiliation(s)
- Hamid Charkhkar
- Electrical and Computer Engineering Department, George Mason University, 4400 University Dr. MSN 1G5, Fairfax, VA 22030, USA.
| | - Susheela Meyyappan
- Department of Bioengineering, George Mason University, 4400 University Dr. MSN 1G5, Fairfax, VA 22030, USA
| | - Evgenia Matveeva
- Adlyfe Inc., 9430 Key West Avenue, Suite 219, Rockville, MD 20850, USA
| | - Jonathan R Moll
- Adlyfe Inc., 9430 Key West Avenue, Suite 219, Rockville, MD 20850, USA
| | - Daniel G McHail
- Department of Molecular Neuroscience, The Krasnow Institute for Advanced Study, George Mason University, Fairfax, VA 22030, USA
| | - Nathalia Peixoto
- Electrical and Computer Engineering Department, George Mason University, 4400 University Dr. MSN 1G5, Fairfax, VA 22030, USA
| | - Richard O Cliff
- System of Systems Analytics, Inc. (SoSACorp), 11250 Waples Mill Road, Fairfax, VA 22030, USA
| | - Joseph J Pancrazio
- Department of Bioengineering, George Mason University, 4400 University Dr. MSN 1G5, Fairfax, VA 22030, USA
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Quarato G, Scrima R, Ripoli M, Agriesti F, Moradpour D, Capitanio N, Piccoli C. Protective role of amantadine in mitochondrial dysfunction and oxidative stress mediated by hepatitis C virus protein expression. Biochem Pharmacol 2014; 89:545-56. [PMID: 24726442 DOI: 10.1016/j.bcp.2014.03.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 03/29/2014] [Accepted: 03/31/2014] [Indexed: 12/16/2022]
Abstract
Amantadine is an antiviral and antiparkinsonian drug that has been evaluated in combination therapies against hepatitis C virus (HCV) infection. Controversial results have been reported concerning its efficacy, and its mechanism of action remains unclear. Data obtained in vitro suggested a role of amantadine in inhibiting HCV p7-mediated cation conductance. In keeping with the fact that mitochondria are responsible to ionic fluxes and that HCV infection impairs mitochondrial function, we investigated a potential role of amantadine in modulating mitochondrial function. Using a well-characterized inducible cell line expressing the full-length HCV polyprotein, we found that amantadine not only prevented but also rescued HCV protein-mediated mitochondrial dysfunction. Specifically, amantadine corrected (i) overload of mitochondrial Ca²⁺; (ii) inhibition of respiratory chain activity and oxidative phosphorylation; (iii) reduction of membrane potential; and (iv) overproduction of reactive oxygen species. The effects of amantadine were observed within 15 min following drug administration and confirmed in Huh-7.5 cells transfected with an infectious HCV genome. These effects were also observed in cells expressing subgenomic HCV constructs, indicating that they are not mediated or only in part mediated by p7. Single organelle analyzes carried out on isolated mouse liver mitochondria demonstrated that amantadine induces hyperpolarization of the membrane potential. Moreover, amantadine treatment increased the calcium threshold required to trigger mitochondrial permeability transition opening. In conclusion, these results support a role of amantadine in preserving cellular bioenergetics and redox homeostasis in HCV-infected cells and unveil an effect of the drug which might be exploited for a broader therapeutic utilization.
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Affiliation(s)
- Giovanni Quarato
- Department of Clinical and Experimental Medicine, University of Foggia, via L. Pinto c/o OO.RR., 71100 Foggia, Italy
| | - Rosella Scrima
- Department of Clinical and Experimental Medicine, University of Foggia, via L. Pinto c/o OO.RR., 71100 Foggia, Italy
| | - Maria Ripoli
- Department of Clinical and Experimental Medicine, University of Foggia, via L. Pinto c/o OO.RR., 71100 Foggia, Italy
| | - Francesca Agriesti
- Laboratory of Pre-Clinical and Translational Research, IRCCS, Referral Cancer Center of Basilicata, Rionero in Vulture, PT, Italy
| | - Darius Moradpour
- Division of Gastroenterology and Hepatology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Nazzareno Capitanio
- Department of Clinical and Experimental Medicine, University of Foggia, via L. Pinto c/o OO.RR., 71100 Foggia, Italy.
| | - Claudia Piccoli
- Department of Clinical and Experimental Medicine, University of Foggia, via L. Pinto c/o OO.RR., 71100 Foggia, Italy.
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Wu SN, Huang HC, Yeh CC, Yang WH, Lo YC. Inhibitory effect of memantine, an NMDA-receptor antagonist, on electroporation-induced inward currents in pituitary GH3 cells. Biochem Biophys Res Commun 2011; 405:508-13. [PMID: 21262200 DOI: 10.1016/j.bbrc.2011.01.066] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 01/19/2011] [Indexed: 10/18/2022]
Abstract
The membrane electroporation-induced inward current (IMEP) in pituitary tumor (GH3) cells was characterized. This current emerges irregularly when membrane hyperpolarizations to -200 mV with a holding potential of -80 mV were elicited. Neither E-4031 (10 μM), glibenclamide (30 μM), nor ZD7288 (30 μM) caused any effects on IMEP. The single-channel conductance and pore radius were estimated to be around 1.12 nS and 1.7 nm, respectively. LaCl3- and memantidine (MEM)-induced block of this current was also examined. The IC50 value for LaCl3- and MEM-induced inhibition of IMEP was 35 and 75 μM, respectively. However, unlike LaCl3, MEM (300 μM) did not exert any effect on voltage-gated Ca2+ current. In inside-out configuration, MEM applied to either external or internal surface of the excised patch did not suppress the activity of ATP-sensitive K+ channels expressed in GH3 cells, although glibenclamide significantly suppressed channel activity. This study provides the first evidence to show that MEM, a non-competitive antagonist of N-methyl D-aspartate receptors, directly inhibits the amplitude of IMEP in pituitary GH3 cells. MEM-mediated block of IMEP in these cells is unlinked to its inhibition of glutamate-induced currents or ATP-sensitive K+ currents. The channel-suppressing properties of MEM might contribute to the underlying mechanisms by which it and its structurally related compounds affect neuronal or neuroendocrine function.
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Affiliation(s)
- Sheng-Nan Wu
- Department of Physiology, National Cheng Kung University Medical College, Tainan City, Taiwan.
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Yu SB, Lim YS, Kim DS. NMDA Receptor Activation Mediates Neuropathic Pain States Induced by Calcium Channel α2δ1 Subunit. Korean J Pain 2009. [DOI: 10.3344/kjp.2009.22.3.210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Soo Bong Yu
- Department of Anesthesiology and Pain Medicine, Kosin University College of Medicine, Busan, Korea
| | - Young Soo Lim
- Department of Anesthesiology and Pain Medicine, Kosin University College of Medicine, Busan, Korea
| | - Doo Sik Kim
- Department of Anesthesiology and Pain Medicine, Kosin University College of Medicine, Busan, Korea
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Giustizieri M, Cucchiaroni ML, Guatteo E, Bernardi G, Mercuri NB, Berretta N. Memantine inhibits ATP-dependent K+ conductances in dopamine neurons of the rat substantia nigra pars compacta. J Pharmacol Exp Ther 2007; 322:721-9. [PMID: 17496164 DOI: 10.1124/jpet.107.122036] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
1-Amino-3,5-dimethyl-adamantane (memantine) is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist used in clinical practice to treat neurodegenerative disorders that could be associated with excitotoxic cell death. Because memantine reduces the loss of dopamine neurons of the substantia nigra pars compacta (SNc) in animal models of Parkinson's disease, we examined the effects of this drug on dopamine cells of the SNc. Besides inhibition of NMDA receptor-mediated currents, memantine (30 and 100 microM) increased the spontaneous firing rate of whole-cell recorded dopamine neurons in a midbrain slice preparation. Occasionally, a bursting activity was observed. These effects were independent from the block of NMDA receptors and were prevented in neurons dialyzed with a high concentration of ATP (10 mM). An increase in firing rate was also induced by the ATP-sensitive potassium (K(ATP)) channel antagonist tolbutamide (300 microM), and this increase occluded further effects of memantine. In addition, K(ATP) channel-mediated outward currents, induced by hypoxia, were inhibited by memantine (30 and 100 microM) in the presence of the NMDA receptor antagonist (5S, 10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) (10 microM). An increase in the spontaneous firing rate by memantine was observed in dopamine neurons recorded with extracellular planar 8 x 8 multielectrodes in conditions of hypoglycemia. These results highlight K(ATP) channels as possible relevant targets of memantine effects in the brain. Moreover, in view of a proposed role of K(ATP) conductances in dopamine neuron degeneration, they suggest another mechanism of action underlying the protective role of memantine in Parkinson's disease.
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Abstract
Most neuroprotective drugs have failed in clinical trials because of side-effects, causing normal brain function to become compromised. A case in point concerns antagonists of the N-methyl-D-aspartate type of glutamate receptor (NMDAR). Glutamate receptors are essential to the normal function of the central nervous system. However, their excessive activation by excitatory amino acids, such as glutamate itself, is thought to contribute to neuronal damage in many neurological disorders ranging from acute hypoxic-ischemic brain injury to chronic neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. The dual role of NMDARs in particular for normal and abnormal functioning of the nervous system imposes important constraints on possible therapeutic strategies aimed at ameliorating neurological diseases. Blockade of excessive NMDAR activity must therefore be achieved without interference with its normal function. In general, NMDAR antagonists can be categorized pharmacologically according to the site of action on the receptor-channel complex. These include drugs acting at the agonist (NMDA) or co-agonist (glycine) sites, channel pore, and modulatory sites, such as the S-nitrosylation site where nitric oxide (NO) reacts with critical cysteine thiol groups. Because glutamate is thought to be the major excitatory transmitter in the brain, generalized inhibition of a glutamate receptor subtype like the NMDAR causes side-effects that clearly limit the potential for clinical applications. Both competitive NMDA and glycine antagonists, even although effective in preventing glutamate-mediated neurotoxicity, will cause generalized inhibition of NMDAR activities and thus have failed in many clinical trials. Open-channel block with the property of uncompetitive antagonism is the most appealing strategy for therapeutic intervention during excessive NMDAR activation as this action of blockade requires prior activation of the receptor. This property, in theory, leads to a higher degree of channel blockade in the presence of excessive levels of glutamate and little blockade at relatively lower levels, for example, during physiological neurotransmission. Utilizing this molecular strategy of action, we review here the logical process that we applied over the past decade to help develop memantine as the first clinically tolerated yet effective agent against NMDAR-mediated neurotoxicity. Phase 3 (final) clinical trials have shown that memantine is effective in treating moderate-to-severe Alzheimer's disease while being well tolerated. Memantine is also currently in trials for additional neurological disorders, including other forms of dementia, glaucoma, and severe neuropathic pain. Additionally, taking advantage of memantine's preferential binding to open channels and the fact that excessive NMDAR activity can be down-regulated by S-nitrosylation, we have recently developed combinatorial drugs called NitroMemantines. These drugs use memantine as a homing signal to target NO to hyperactivated NMDARs in order to avoid systemic side-effects of NO such as hypotension (low blood pressure). These second-generation memantine derivatives are designed as pathologically activated therapeutics, and in preliminary studies appear to have even greater neuroprotective properties than memantine.
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Affiliation(s)
- Huei-Sheng Vincent Chen
- Burnham Institute for Medical Research and the University of California-San Diego, La Jolla, California 92037, USA.
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Fischer W. Anticonvulsant profile and mechanism of action of propranolol and its two enantiomers. Seizure 2002; 11:285-302. [PMID: 12076101 DOI: 10.1053/seiz.2001.0644] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The anticonvulsant properties of the ss-adrenoceptor antagonist propranolol and its two enantiomers were examined in various screening tests in order to characterize the anticonvulsant profile as well as the possible molecular mechanism of action. These compounds dose-dependently raised the threshold for tonic electroshock seizures in mice and were effective in the traditional maximal electroshock test (ED (50)s 15- 20 mg kg (-1)i.p.). In combination with clinically used antiepileptics, the anticonvulsant effectiveness of the latter was significantly increased. In the pentylenetetrazol (85 mg kg (-1)s.c.) seizure threshold test, ( +/-)- and ( +)-propranolol were not effective in preventing clonic seizures. In unrestrained rats with chronically implanted electrodes in the dorsal hippocampus, propranolol and its ( +)-enantiomer equieffectively reduced the duration of electrically-evoked hippocampal afterdischarges (10 and 20 mg kg (-1)i.p.) and raised the focal stimulation threshold (20 mg kg (-1)i.p.). In amygdala-kindled rats, both drugs ( >or= 10 mg kg (-1)i.p.) reduced the seizure severity from stage 5 (generalized clonic-tonic) to stage 3 (unilateral forelimb) seizures. Furthermore, whole-cell patch-clamp experiments showed that ( +)- as well as ( -)-propranolol ( 10(-6)to 10(-4)M) depressed the fast inward sodium current in a concentration- and use-dependent manner in cultured rat cardiomyocytes and inhibited picrotoxin-induced burst firing activity of mouse spinal cord neurones in culture. In conclusion, propranolol and its two enantiomers have anticonvulsant effects in models for generalized tonic-clonic and complex partial seizures which may be accounted for by the sodium channel blocking and not by the ss-adrenoceptor blocking activity.
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Affiliation(s)
- W Fischer
- Rudolf-Boehm-Institute of Pharmacology and Toxicology, University of Leipzig, Leipzig, Germany.
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Parsons CG, Danysz W, Quack G. Memantine is a clinically well tolerated N-methyl-D-aspartate (NMDA) receptor antagonist--a review of preclinical data. Neuropharmacology 1999; 38:735-67. [PMID: 10465680 DOI: 10.1016/s0028-3908(99)00019-2] [Citation(s) in RCA: 614] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
N-methyl-D-aspartate (NMDA) receptor antagonists have therapeutic potential in numerous CNS disorders ranging from acute neurodegeneration (e.g. stroke and trauma), chronic neurodegeneration (e.g. Parkinson's disease, Alzheimer's disease, Huntington's disease, ALS) to symptomatic treatment (e.g. epilepsy, Parkinson's disease, drug dependence, depression, anxiety and chronic pain). However, many NMDA receptor antagonists also produce highly undesirable side effects at doses within their putative therapeutic range. This has unfortunately led to the conclusion that NMDA receptor antagonism is not a valid therapeutic approach. However, memantine is clearly an uncompetitive NMDA receptor antagonist at therapeutic concentrations achieved in the treatment of dementia and is essentially devoid of such side effects at doses within the therapeutic range. This has been attributed to memantine's moderate potency and associated rapid, strongly voltage-dependent blocking kinetics. The aim of this review is to summarise preclinical data on memantine supporting its mechanism of action and promising profile in animal models of chronic neurodegenerative diseases. The ultimate purpose is to provide evidence that it is indeed possible to develop clinically well tolerated NMDA receptor antagonists, a fact reflected in the recent interest of several pharmaceutical companies in developing compounds with similar properties to memantine.
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Affiliation(s)
- C G Parsons
- Department of Pharmacological Research, Merz and Co., Frankfurt am Main, Germany.
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9
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Albrecht-Goepfert E, Schempp H, Elstner EF. Modulation of the production of reactive oxygen species by pre-activated neutrophils by aminoadamantane derivatives. Biochem Pharmacol 1998; 56:141-52. [PMID: 9698098 DOI: 10.1016/s0006-2952(98)00024-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Aminoadamantane derivatives (AAD) such as amantadine or memantine have been used for the treatment of Morbus Parkinson and Morbus Alzheimer. In this communication, we report on the immunomodulatory activities of AAD. Luminol-dependent chemiluminescence of zymosan-, N-formylmethionylleucylphenylalanine(FMLP)- or experimental Ca2+-ionophore(A 231879)-preactivated polymorphonuclear leukocytes (PMN) was strongly enhanced by submicromolar concentrations of AAD and inhibited at higher concentrations than 0.1 mM. Light emission by phorbol-12-myristate-acetate(PMA)-preactivated cells was not further stimulated but inhibited by the elevated concentrations, just as with the other, above-mentioned activators. Ethylene formation from alpha-keto-methylthiobutyrate (KMB) as an indicator for production of OH.-type reactive oxygen species by the NADPH-oxidase ("respiratory burst") was augmented by AAD and completely inhibited by superoxide dismutase. In contrast, ethylene release from 1-amino-cyclopropyl-l-carboxylic acid (ACC) as relatively specific indicator for the myeloperoxidase reaction after degranulation was not influenced by AAD. As documented by several model reactions, AAD per se did not act as scavengers or quenchers of activated oxygen species such as superoxide, OH.-radical, hydrogen peroxide or hypochlorite. Altogether, these results suggest that submicromolar concentrations of AAD upregulate the respiratory burst, but apparently not the degranulation of prestimulated polymorphonuclear leukocytes. At higher concentrations of AAD, both respiratory burst and degranulation are inhibited, however. These effects can also be shown in complete blood samples.
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Affiliation(s)
- E Albrecht-Goepfert
- Technische Universität München, Lehrstuhl für Phytopathologie, (Labor F.Angewandte Biochemie), Freising, Germany
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Apland JP, Cann FJ. Anticonvulsant effects of memantine and MK-801 in guinea pig hippocampal slices. Brain Res Bull 1995; 37:311-6. [PMID: 7627576 DOI: 10.1016/0361-9230(95)00038-g] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The anticonvulsant properties of memantine (Mem) were compared to those of MK-801. Extracellular field recordings were obtained from area CA1 of guinea pig hippocampal slices in a total submersion chamber at 32 degrees C in normal oxygenated artificial cerebrospinal fluid (ACSF). Evoked responses were elicited by 0.07 Hz stimulation of the Schaffer collateral and commissural fibers. Bath perfusion of slices with Mg(2+)-free ACSF and N-methyl-D-aspartate (NMDA)-containing ACSF induced epileptiform afterdischarges following evoked responses. Pretreatment of slices by bath application of 100 microM Mem for 18-20 min prevented epileptiform afterdischarges under both convulsant conditions. Perfusion with 100 microM Mem alone for up to 50 min had no discernible effect on evoked responses. MK-801 was as effective at < or = 10 microM and required application for over 15 min to suppress afterdischarges completely. Both Mem and MK-801 suppressed epileptiform activity when applied after such activity was induced by NMDA or MG(2+)-free ACSF. The EC50 of Mem was 16.6 microM and that of MK-801 was 0.19 microM for blocking NMDA-induced evoked response suppression. Thus, in the guinea pig hippocampal slice preparation, Mem appeared to have anticonvulsant properties qualitatively similar to those of MK-801, but was 10-100 fold less potent.
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Affiliation(s)
- J P Apland
- Neurotoxicology Branch, U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5425, USA
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McLean MJ, Gupta RC, Dettbarn WD, Wamil AW. Prophylactic and therapeutic efficacy of memantine against seizures produced by soman in the rat. Toxicol Appl Pharmacol 1992; 112:95-103. [PMID: 1733053 DOI: 10.1016/0041-008x(92)90284-y] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Male Sprague-Dawley rats injected sc with a single sublethal dose of the organophosphate nerve agent, soman (100 micrograms/kg), had motor limbic seizures within 5-15 min. Pretreatment with a single dose of memantine HCl (MEM, 18 mg/kg, sc), alone or in combination with atropine sulfate (ATS, 16 mg/kg, sc), before soman prevented seizures without sedation or ataxia. Rats appeared normal or demonstrated increased exploratory activity. Excessive salivation, a peripheral manifestation of soman intoxication, was decreased by ATS, but pretreatment with ATS alone did not prevent seizures. After seizure onset, MEM +/- ATS, but not ATS, abolished seizures. Acetylcholinesterase (AChE) activity in several brain regions (cortex, stem, striatum, and hippocampus) was markedly reduced by soman, but not by MEM, ATS, or MEM + ATS. Preadministration of MEM + ATS in vivo significantly protected AChE from inhibition by soman. Memantine reduced inhibition of AChE activity in crude brain homogenates by soman, but not by edrophonium (anionic site inhibitor) or decamethonium (peripheral site inhibitor). Thus, MEM may bind to a different modulatory site, not yet characterized, to protect AChE. When given after onset of soman-induced seizures, treatment with MEM +/- ATS did not reactivate AChE although seizures were controlled, suggesting additional anticonvulsant mechanisms of action. At concentrations (10(-4) to 5 x 10(-4) M) which did not significantly alter the spontaneous firing of action potentials (APs), MEM limited sustained high frequency repetitive firing (SRF) induced by depolarization of spinal cord (mouse and rat) and neocortical (mouse) neurons in monolayer-dissociated cell culture. In the same range of concentrations, ATS both limited SRF and suppressed spontaneous activity, suggesting toxicity. In addition, MEM and ATS reversibly produced use-dependent block of depolarizing responses to acetylcholine (ACh) applied by pressure ejection to spinal cord neurons. Thus, the anticonvulsant efficacy of MEM, with or without ATS, may have resulted from a combination of actions, including protection of AChE from inhibition by soman, limitation of high frequency firing of APs, and blockade of excitatory postsynaptic responses to ACh.
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Affiliation(s)
- M J McLean
- Department of Neurology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232
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