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Okamura T, Tsukamoto S, Okada M, Kikuchi T, Aizawa R, Wakizaka H, Nengaki N, Ogawa M, Ishii H, Zhang MR. 11C-Labeled Radiotracer for Noninvasive and Quantitative Assessment of the Thiocyanate Efflux System in the Brain. Bioconjug Chem 2022; 33:1654-1662. [PMID: 35951365 DOI: 10.1021/acs.bioconjchem.2c00277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Thiocyanate (SCN-) alters the potency of certain agonists for the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, and dysfunctions in AMPA receptor signaling are considered to underlie a number of neurological diseases. While humans may be exposed to SCN- from the environment, including food sources, a carrier-mediated system transports SCN- from the brain into the blood and is an important regulator of SCN- distribution in the central nervous system. The assessment of this SCN- efflux system in the brain would thus be useful for understanding the mechanisms underlying the neurotoxicity of SCN- and for elucidating the relationship between the efflux system and brain diseases. However, the currently available technique for studying SCN- efflux is severely limited by its invasiveness. Here, we describe the development of a SCN- protracer, 9-pentyl-6-[11C]thiocyanatopurine ([11C]1), to overcome this limitation. [11C]1 was synthesized by the reaction of the iodo-precursor and [11C]SCN- or the reaction of the disulfide precursor with [11C]NH4CN. The protracer [11C]1 entered the brain after intravenous injection into mice and was rapidly metabolized to [11C]SCN-, which was then eliminated from the brain. The efflux of [11C]SCN- was dose-dependently inhibited by perchlorate, a monovalent anion, and the highest dose caused an 82% reduction in the efflux rate. Our findings demonstrate that [11C]1 can be used for the noninvasive and quantitative assessment of the SCN- efflux system in the brain.
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Affiliation(s)
- Toshimitsu Okamura
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Satoshi Tsukamoto
- Laboratory of Animal and Genome Sciences Section, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Maki Okada
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Tatsuya Kikuchi
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Ryutaro Aizawa
- Laboratory of Animal and Genome Sciences Section, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Hidekatsu Wakizaka
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Nobuki Nengaki
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.,SHI Accelerator Service, Ltd., 1-17-6 Osaki, Shinagawa-ku, Tokyo 141-0032, Japan
| | - Masanao Ogawa
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.,SHI Accelerator Service, Ltd., 1-17-6 Osaki, Shinagawa-ku, Tokyo 141-0032, Japan
| | - Hideki Ishii
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
| | - Ming-Rong Zhang
- Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, National Institutes for Quantum Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
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2
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Baguma M, Nzabara F, Maheshe Balemba G, Malembaka EB, Migabo C, Mudumbi G, Bito V, Cliff J, Rigo JM, Chabwine JN. Konzo risk factors, determinants and etiopathogenesis: What is new? A systematic review. Neurotoxicology 2021; 85:54-67. [PMID: 33964344 DOI: 10.1016/j.neuro.2021.05.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 05/01/2021] [Accepted: 05/03/2021] [Indexed: 12/13/2022]
Abstract
Konzo is a toxico-nutritional upper motor neuron disease causing a spastic paraparesis in schoolchildren and childbearing women in some African countries. Almost a century since the first description of konzo, its underlying etiopathogenic mechanisms and causative agent remain unknown. This paper aims at refreshing the current knowledge of konzo determinants and pathogenesis in order to enlighten potential new research and management perspectives. Literature research was performed in PubMed and Web of Science databases according to the PRISMA methodology. Available data show that cassava-derived cyanide poisoning and protein malnutrition constitute two well-documented risk factors of konzo. However, observational studies have failed to demonstrate the causal relationship between konzo and cyanide poisoning. Thiocyanate, the current marker of choice of cyanide exposure, may underestimate the actual level of cyanide poisoning in konzo patients as a larger amount of cyanide is detoxified via other unusual pathways in the context of protein malnutrition characterizing these patients. Furthermore, the appearance of konzo may be the consequence of the interplay of several factors including cyanide metabolites, nutritional deficiencies, psycho-emotional and geo-environmental factors, resulting in pathophysiologic phenomena such as excitotoxicity or oxidative stress, responsible for neuronal damage that takes place at sparse cellular and/or subcellular levels.
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Affiliation(s)
- Marius Baguma
- Department of Internal Medicine, Hôpital Provincial Général de Référence de Bukavu (HPGRB), Université Catholique de Bukavu (UCB), Bukavu, Democratic Republic of the Congo; Biomedical Research Institute (BIOMED), UHasselt - Hasselt University, Agoralaan, 3590 Diepenbeek, Belgium.
| | - Fabrice Nzabara
- Department of Internal Medicine, Hôpital Provincial Général de Référence de Bukavu (HPGRB), Université Catholique de Bukavu (UCB), Bukavu, Democratic Republic of the Congo; École Régionale de Santé Publique (ERSP), Université Catholique de Bukavu (UCB), Bukavu, Democratic Republic of the Congo
| | - Ghislain Maheshe Balemba
- Department of Internal Medicine, Hôpital Provincial Général de Référence de Bukavu (HPGRB), Université Catholique de Bukavu (UCB), Bukavu, Democratic Republic of the Congo
| | - Espoir Bwenge Malembaka
- École Régionale de Santé Publique (ERSP), Université Catholique de Bukavu (UCB), Bukavu, Democratic Republic of the Congo
| | - Christiane Migabo
- Faculty of Agronomy, Université Catholique de Bukavu (UCB), Bukavu, Democratic Republic of the Congo; Department of Geography and Environmental Studies, College of Social Sciences and Humanities, Jimma University, Jimma, Ethiopia
| | - Germain Mudumbi
- Department of Pediatrics, Hôpital Provincial Général de Référence de Bukavu (HPGRB), Université Catholique de Bukavu (UCB), Bukavu, Democratic Republic of the Congo
| | - Virginie Bito
- Biomedical Research Institute (BIOMED), UHasselt - Hasselt University, Agoralaan, 3590 Diepenbeek, Belgium
| | - Julie Cliff
- Faculty of Medicine, Department of Community Health, Eduardo Mondlane University, Maputo, Mozambique
| | - Jean-Michel Rigo
- Biomedical Research Institute (BIOMED), UHasselt - Hasselt University, Agoralaan, 3590 Diepenbeek, Belgium
| | - Joëlle Nsimire Chabwine
- Department of Internal Medicine, Hôpital Provincial Général de Référence de Bukavu (HPGRB), Université Catholique de Bukavu (UCB), Bukavu, Democratic Republic of the Congo; Department of Neuroscience and Movement Science, Faculty of Science and Medicine, University of Fribourg, Fribourg, Switzerland
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3
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The Acute Encephalopathy Induced by Intake of Sugihiratake Mushroom in the Patients with Renal Damage Might Be Associated with the Intoxication of Cyanide and Thiocyanate. Food Saf (Tokyo) 2015. [DOI: 10.14252/foodsafetyfscj.2014036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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4
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Sawant PM, Tyndall JDA, Holland PT, Peake BM, Mountfort DO, Kerr DS. In vivo seizure induction and affinity studies of domoic acid and isodomoic acids-D, -E and -F. Neuropharmacology 2010; 59:129-38. [PMID: 20416329 DOI: 10.1016/j.neuropharm.2010.03.019] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 03/15/2010] [Accepted: 03/31/2010] [Indexed: 11/20/2022]
Abstract
Domoic acid and its isomers are produced via algal blooms and are found in high concentrations in shellfish. Here, we assessed the acute seizurogenic potencies of isomers-D, -E and -F and their binding affinities at heterogeneous populations of KA receptors from rat cerebrum. In addition, binding affinities of all six isomers (Iso-A through -F) were assessed at AMPA receptors. Radioligand displacement studies indicated that the seizurogenic potency of Iso-F (E-configuration) closely correlates with its affinities at both KA and AMPA receptors, whereas isomers-D (Z) and -E (E), which exhibit distinctly lower seizurogenic potencies, are quite weak displacers. Previously observed functional potencies for isomers-A, -B and -C (Sawant et al., 2008) correlated with AMPA receptor affinities observed here. Taken together, these findings call into question previous structure-activity rules. Significantly, in our hands, Iso-D was ten-fold less potent than Iso-F. To further explain observed links between structural conformation and functional potency, molecular modeling was employed. Modeling results closely matched the rank order of potency and binding data observed. We further assessed the efficacy of isomers-D, -E and -F as pharmacological preconditioning agents. Acute preconditioning with low-dose Iso-D, -E or -F, before high-dose DA failed to impart behavioural tolerance. This study has shed new light on structural conformations affecting non-NMDA ionotropic glutamate receptor binding and functional potency, and provides a foundation for future work in areas of AMPA and KA receptor modeling.
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Affiliation(s)
- P M Sawant
- Department of Pharmacology and Toxicology, University of Otago School of Medical Sciences, Dunedin, New Zealand.
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5
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Kovács I, Simon A, Szárics E, Barabás P, Héja L, Nyikos L, Kardos J. Cyclothiazide binding to functionally active AMPA receptor reveals genuine allosteric interaction with agonist binding sites. Neurochem Int 2004; 44:271-80. [PMID: 14602090 DOI: 10.1016/s0197-0186(03)00137-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The agonist, [3H](-)[S]-1-(2-amino-2-carboxyethyl)-5-fluoro-pyrimidine-2,4-dione ([3H](S)F-Willardiine) binding to functional alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors of resealed plasma membrane vesicles and nerve endings freshly isolated from the rat cerebral cortex displayed two binding sites (K(D1)=33+/-7 nM, B(MAX1)=1.6+/-0.3 pmol/mg protein, K(D2)=720+/-250 nM and B(MAX2)=7.8+/-4.0 pmol/mg protein). The drug which impairs AMPA receptor desensitisation, 6-chloro-3,4-dihydro-3-(2-norbornene-5-yl)-2H-1,2,4-benzothiadiazine-7-sulphonamide-1,1-dioxide (cyclothiazide, CTZ) fully displaced the [3H](S)F-Willardiine binding at a concentration of 500 microM. In the presence of 100 microM CTZ (K(I(CTZ))=60+/-6 microM), both the antagonist [3H]-1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo(F)quinoxaline-7-sulfonamide ([3H]NBQX: K(D)=24+/-4 nM, B(MAX)=12.0+/-0.1 pmol/mg protein) and the high-affinity agonist binding showed similar affinity reduction ([3H](S)F-Willardiine: K(D)=140+/-19 nM, B(MAX)=2.9+/-0.5 pmol/mg protein; [3H]NBQX: K(D)=111+/-34 nM, B(MAX)=12+/-3 pmol/mg protein). To disclose structural correlates underlying genuine allosteric binding interactions, molecular mechanics calculations of CTZ-induced structural changes were performed with the use of PDB data on extracellular GluR2 binding domain dimeric crystals available by now. Hydrogen-bonding and root mean square (rms) values of amino acid residues recognising receptor agonists showed minor alterations in the agonist binding sites itself. Moreover, CTZ binding did not affect dimeric subunit structures significantly. These findings indicated that the structural changes featuring the non-desensitised state could possibly occur to a further site of the extracellular GluR2 binding domain. The increase of agonist efficacy on allosteric CTZ binding may be interpreted in terms of a mechanism involving AMPA receptor desensitisation sequential to activation.
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Affiliation(s)
- Ilona Kovács
- Department of Neurochemistry, Chemical Research Center, Hungarian Academy of Sciences, 1025 Pusztaszeri út 59-67, Budapest, Hungary.
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6
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Allison C, Pratt JA. Neuroadaptive processes in GABAergic and glutamatergic systems in benzodiazepine dependence. Pharmacol Ther 2003; 98:171-95. [PMID: 12725868 DOI: 10.1016/s0163-7258(03)00029-9] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Knowledge of the neural mechanisms underlying the development of benzodiazepine (BZ) dependence remains incomplete. The gamma-aminobutyric acid (GABA(A)) receptor, being the main locus of BZ action, has been the main focus to date in studies performed to elucidate the neuroadaptive processes underlying BZ tolerance and withdrawal in preclinical studies. Despite this intensive effort, however, no clear consensus has been reached on the exact contribution of neuroadaptive processes at the level of the GABA(A) receptor to the development of BZ tolerance and withdrawal. It is likely that changes at the level of this receptor are inadequate in themselves as an explanation of these neuroadaptive processes and that neuroadaptations in other receptor systems are important in the development of BZ dependence. In particular, it has been hypothesised that as part of compensatory mechanisms to diazepam-induced chronic enhancement of GABAergic inhibition, excitatory mechanisms (including the glutamatergic system) become more sensitive [Behav. Pharmacol. 6 (1995) 425], conceivably contributing to BZ tolerance development and/or expression of withdrawal symptoms on cessation of treatment, including increased anxiety and seizure activity. Glutamate is a key candidate for changes in excitatory transmission mechanisms and BZ dependence, (1) since there are defined neuroanatomical relationships between glutamatergic and GABAergic neurons in the CNS and (2) because of the pivotal role of glutamatergic neurotransmission in mediating many forms of synaptic plasticity in the CNS, such as long-term potentiation and kindling events. Thus, it is highly possible that glutamatergic processes are also involved in the neuroadaptive processes in drug dependence, which can conceivably be considered as a form of synaptic plasticity. This review provides an overview of studies investigating changes in the GABAergic and glutamatergic systems in the brain associated with BZ dependence, with particular attention to the possible differential involvement of N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors in these processes.
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Affiliation(s)
- C Allison
- Department of Physiology and Pharmacology, Strathclyde Institute for Biomedical Sciences, University of Strathclyde, Taylor Street, G4 ONR, Glasgow, UK
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7
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Silverdale MA, Crossman AR, Brotchie JM. Striatal AMPA receptor binding is unaltered in the MPTP-lesioned macaque model of Parkinson's disease and dyskinesia. Exp Neurol 2002; 174:21-8. [PMID: 11869030 DOI: 10.1006/exnr.2001.7854] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Long-term levodopa or dopamine agonist treatment in the MPTP-lesioned primate model of Parkinson's disease elicits dyskinesia, which is phenotypically similar to levodopa-induced dyskinesia in patients with Parkinson's disease. AMPA receptor antagonists have previously been shown to have both anti-parkinsonian and anti-dyskinetic actions in MPTP-lesioned primates, suggesting that AMPA receptor transmission is functionally overactive under these conditions. In this study, we investigated the level of striatal AMPA receptor binding in the MPTP lesioned primate using the selective AMPA ligand (3)H-(S)-5-fluorowillardiine. AMPA receptor binding was studied in non-parkinsonian, non-dyskinetic parkinsonian, and dyskinetic macaques. Striatal AMPA receptor binding was not different in any of the treatment groups (P > 0.05). Although AMPA receptor-mediated transmission is functionally overactive in Parkinson's disease and dyskinesia, changes in striatal AMPA receptor levels are not likely to be the cause of such movement disorders.
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MESH Headings
- 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine
- Alanine/analogs & derivatives
- Alanine/pharmacology
- Animals
- Apomorphine/adverse effects
- Apomorphine/pharmacology
- Autoradiography
- Binding, Competitive/drug effects
- Corpus Striatum/drug effects
- Corpus Striatum/metabolism
- Corpus Striatum/pathology
- Disease Models, Animal
- Dyskinesia, Drug-Induced/etiology
- Dyskinesia, Drug-Induced/metabolism
- Excitatory Amino Acid Agonists/pharmacology
- Female
- Ligands
- Macaca mulatta
- Male
- Organ Specificity
- Parkinson Disease, Secondary/chemically induced
- Parkinson Disease, Secondary/complications
- Parkinson Disease, Secondary/metabolism
- Parkinson Disease, Secondary/pathology
- Pyrimidines/pharmacology
- Radioligand Assay
- Receptors, AMPA/metabolism
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Affiliation(s)
- M A Silverdale
- Manchester Movement Disorders Laboratory, Manchester, United Kingdom
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8
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Bräuner-Osborne H, Egebjerg J, Nielsen EO, Madsen U, Krogsgaard-Larsen P. Ligands for glutamate receptors: design and therapeutic prospects. J Med Chem 2000; 43:2609-45. [PMID: 10893301 DOI: 10.1021/jm000007r] [Citation(s) in RCA: 435] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
MESH Headings
- Animals
- Drug Design
- Excitatory Amino Acid Agonists/chemistry
- Excitatory Amino Acid Agonists/metabolism
- Excitatory Amino Acid Agonists/pharmacology
- Excitatory Amino Acid Agonists/therapeutic use
- Excitatory Amino Acid Antagonists/chemistry
- Excitatory Amino Acid Antagonists/metabolism
- Excitatory Amino Acid Antagonists/pharmacology
- Excitatory Amino Acid Antagonists/therapeutic use
- Humans
- Ligands
- N-Methylaspartate/agonists
- N-Methylaspartate/antagonists & inhibitors
- N-Methylaspartate/chemistry
- N-Methylaspartate/metabolism
- Receptors, AMPA/agonists
- Receptors, AMPA/antagonists & inhibitors
- Receptors, AMPA/chemistry
- Receptors, AMPA/metabolism
- Receptors, Glutamate/chemistry
- Receptors, Glutamate/drug effects
- Receptors, Glutamate/metabolism
- Receptors, Kainic Acid/agonists
- Receptors, Kainic Acid/antagonists & inhibitors
- Receptors, Kainic Acid/chemistry
- Receptors, Kainic Acid/metabolism
- Receptors, Metabotropic Glutamate/agonists
- Receptors, Metabotropic Glutamate/antagonists & inhibitors
- Receptors, Metabotropic Glutamate/chemistry
- Receptors, Metabotropic Glutamate/metabolism
- Synapses/metabolism
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Affiliation(s)
- H Bräuner-Osborne
- NeuroScience PharmaBiotec Research Center, Department of Medicinal Chemistry, The Royal Danish School of Pharmacy, DK-2100 Copenhagen, Denmark
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Cai SX, Huang JC, Espitia SA, Tran M, Ilyin VI, Hawkinson JE, Woodward RM, Weber E, Keana JF. 5-(N-oxyaza)-7-substituted-1,4-dihydroquinoxaline-2,3-diones: novel, systemically active and broad spectrum antagonists for NMDA/glycine, AMPA, and kainate receptors. J Med Chem 1997; 40:3679-86. [PMID: 9357535 DOI: 10.1021/jm970396y] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A group of 5-aza-7-substituted-1,4-dihydroquinoxaline-2,3-diones (QXs) and the corresponding 5-(N-oxyaza)-7-substituted QXs were prepared and evaluated as antagonists of ionotropic glutamate receptors. The in vitro potency of these QXs was determined by inhibition of [3H]-5,7-dichlorokynurenic acid ([3H]DCKA) binding to N-methyl-D-aspartate (NMDA)/glycine receptors, [3H]-(S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid ([3H]AMPA) binding to AMPA receptors, and [3H]kainate ([3H]KA) binding to KA receptors in rat brain membranes. 5-(N-Oxyaza)-QXs 12a-e all have low micromolar or submicromolar potency for NMDA/glycine receptors and low micromolar potencies for AMPA and KA receptors. QXs 12a-e display 2-12-fold selectivity for NMDA/glycine receptors compared to AMPA receptors, and approximately 2-fold difference between AMPA and KA potency. In contrast to other QXs that either show high selectivity for NMDA (such as ACEA 1021) or AMPA (such as NBQX) receptors, these molecules are broad spectrum antagonists of ionotropic glutamate receptors. 7-Nitro-5-(N-oxyaza)-QX (12e) is the most potent inhibitor among 12a-e, having IC50 values of 0.69, 1.3, and 2.4 microM at NMDA, AMPA, and KA receptors, respectively. In functional assays on glutamate receptors expressed in oocytes by rat cerebral cortex poly(A+) RNA, 7-chloro-5-(N-oxyaza)-QX (12a) and 7-nitro-5-(N-oxyaza)-QX (12e) have Kb values of 0.63 and 0.31 microM for NMDA/glycine receptors, and are 6- and 4-fold selective for NMDA over AMPA receptors, respectively. 5-(N-Oxyaza)-7-substituted-QXs 12a-e all have surprisingly high in vivo potency as anticonvulsants in a mouse maximal electroshock-induced seizure (MES) model. 7-Chloro-5-(N-oxyaza)-QX (12a), 7-bromo-5-(N-oxyaza)-QX (12b), and 7-methyl-5-(N-oxyaza)-QX (12c) have ED50 values of 0.82, 0.87, and 0.97 mg/kg i.v., respectively. The high in vivo potency of QXs 12a-e is particularly surprising given their low log P values (approximately -2.7). Separate studies indicate that QXs 12a and 12e are also active in vivo as neuroprotectants and also have antinociceptive activity in animal pain models. In terms of in vivo activity, these 5-(N-oxyaza)-7-substituted-QXs are among the most potent broad spectrum ionotropic glutamate antagonists reported.
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Affiliation(s)
- S X Cai
- CoCensys Inc., Irvine, California 92618, USA
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