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Povl Krogsgaard-larsen - One of the best experts on this subject based on the ideXlab platform.

  • Tetrazolyl isoxazole amino Acids as ionotropic glutamate Receptor antagonists: Synthesis, modelling and molecular pharmacology
    Bioorganic & Medicinal Chemistry, 2005
    Co-Authors: Bente Frølund, Tine B. Stensbøl, Ulf Madsen, Mai Marie Holm, Jeremy R. Greenwood, Jan Egebjerg, Hans Bräuner-osborne, Birgitte Nielsen, Povl Krogsgaard-larsen
    Abstract:

    Abstract Two 3-(5-tetrazolylmethoxy) analogues, 1a and 1b , of ( RS )-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic Acid (AMPA), a selective AMPA Receptor agonist, and ( RS )-2-amino-3-(5- tert -butyl-3-hydroxy-4-isoxazolyl)propionic Acid (ATPA), a GluR5-preferring agonist, were synthesized. Compounds 1a and 1b were pharmacologically characterized in Receptor binding assays, and electrophysiologically on homomeric AMPA Receptors (GluR1-4), homomeric (GluR5 and GluR6) and heteromeric (GluR6/KA2) Kainic Acid Receptors, using two-electrode voltage-clamped Xenopus laevis oocytes expressing these Receptors. Both analogues proved to be antagonists at all AMPA Receptor subtypes, showing potencies ( K b  = 38–161 μM) similar to that of the AMPA Receptor antagonist ( RS )-2-amino-3-[3-(carboxymethoxy)-5-methyl-4-isoxazolyl]propionic Acid (AMOA) ( K b  = 43–76 μM). Furthermore, the AMOA analogue, 1a , blocked two Kainic Acid Receptor subtypes (GluR5 and GluR6/KA2), showing sevenfold preference for GluR6/KA2 ( K b  = 19 μM). Unlike the iGluR antagonist ( S )-2-amino-3-[5- tert -butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic Acid [( S )-ATPO], the corresponding tetrazolyl analogue, 1b , lacks Kainic Acid Receptor effects. On the basis of docking to a crystal structure of the isolated extracellular ligand-binding core of the AMPA Receptor subunit GluR2 and a homology model of the Kainic Acid Receptor subunit GluR5, we were able to rationalize the observed structure–activity relationships.

  • Synthesis and Receptor binding affinity of new selective GluR5 ligands.
    Bioorganic & medicinal chemistry, 2001
    Co-Authors: Lennart Bunch, Tine B. Stensbøl, Povl Krogsgaard-larsen, Tommy N Johansen, Hans Bräuner-osborne, Tina H. Johansen, Ulf Madsen
    Abstract:

    Abstract Two hybrid analogues of the Kainic Acid Receptor agonists, 2-amino-3-(5- tert -butyl-3-hydroxy-4-isoxazolyl)propionic Acid (ATPA) and (2 S ,4 R )-4-methylglutamic Acid ((2 S ,4 R )-4-Me-Glu), were designed, synthesized, and characterized in radioligand binding assays using cloned ionotropic and metabotropic glutamic Acid Receptors. The ( S )-enantiomers of E -4-(2,2-dimethylpropylidene)glutamic Acid (( S )- 1 ) and E -4-(3,3-dimethylbutylidene)glutamic Acid (( S )- 2 ) were shown to be selective and high affinity GluR5 ligands, with K i values of 0.024 and 0.39 μM, respectively, compared to K i values at GluR2 of 3.0 and 2.0 μM, respectively. Their affinities in the [ 3 H]AMPA binding assay on native cortical Receptors were shown to correlate with their GluR2 affinity rather than their GluR5 affinity. No affinity for GluR6 was detected (IC 50 >100 μM).

  • Structural Determinants of AMPA Agonist Activity in Analogues of 2-Amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionic Acid: Synthesis and Pharmacology
    Journal of Medicinal Chemistry, 2000
    Co-Authors: Benny Bang-andersen, Tine B. Stensbøl, Sibylle Moltzen Lenz, Haleh Ahmadian, Klaus Peter Bogeso, Ulf Madsen, Povl Krogsgaard-larsen
    Abstract:

    We have previously shown that the 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic Acid (AMPA) Receptor agonist, 2-amino-3-(3-carboxy-5-methyl-4-isoxazolyl)propionic Acid (ACPA, 2), binds to AMPA Receptors in a manner different from that of AMPA (1) itself and that 2, in contrast to 1, also binds to Kainic Acid Receptor sites. To elucidate the structural requirements for selective activation of the site/conformation of AMPA Receptors recognized by 2, a number of isosteric analogues of 2 have now been synthesized and pharmacologically characterized. The compound 2-amino-3-(5-carboxy-3-methoxy-4-isoxazolyl)propionic Acid (3a) (IC50 = 0.11 μM; EC50 = 1.2 μM), which is a regioisostere of 2 with a methoxy group substituted for the methyl group, was approximately equipotent with 2 (IC50 = 0.020 μM; EC50 = 1.0 μM) as an inhibitor of [3H]AMPA binding and as an AMPA agonist, respectively, whereas the corresponding 3-ethoxy analogue 3b (IC50 = 1.0 μM; EC50 = 4.8 μM) was slightly weaker. The analogues 3c−e, cont...

  • Synthesis of deuterium and tritium labelled (RS)-2-Amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)-propionic Acid (ATPA), a selective Kainic Acid Receptor agonist
    Journal of Labelled Compounds and Radiopharmaceuticals, 1999
    Co-Authors: Tommy N Johansen, Tine B. Stensbøl, Bjarke Ebert, Calvin R. Hawes, Gareth J. Ellis, Dorthe Da Graça Thrige, Povl Krogsgaard-larsen
    Abstract:

    (RS)-2-Amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic Acid (ATPA) is an excitatory amino Acid Receptor agonist showing selectivity for the Kainic Acid Receptor subtype GluR5. As part of the pharmacological characterization of GluR5 Receptors, we now report the synthesis of [ 3 H]ATPA based on a four-step synthesis using 5-tert-butyl-3-methoxy-4-isoxazolylcarbaldehyde as the starting material. Using this synthetic procedure deuterium and tritium labelled ATPA have been prepared. [ 3 H]ATPA, with a specific activity of 17 Ci/mmol, was obtained with a radiochemical purity of 98.9%. Attempts to demonstrate specific binding of [ 3 H]ATPA under conventional rat brain membrane Receptor binding conditions were unsuccessful.

  • AMPA Receptor agonists: resolution, configurational assignment, and pharmacology of (+)-(S)- and (-)-(R)-2-amino-3-[3-hydroxy-5-(2-pyridyl)-isoxazol-4-yl]-propionic Acid (2-Py-AMPA).
    Chirality, 1997
    Co-Authors: Tommy N Johansen, Erik Falch, Bjarke Ebert, Povl Krogsgaard-larsen
    Abstract:

    We have previously shown that whereas (RS)-2-amino-3-(3-hydroxy-5-phenylisoxazol-4-yl)propionic Acid (APPA) shows the characteristics of a partial agonist at (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic Acid (AMPA) Receptors, (S)-APPA is a full AMPA Receptor agonist and (R)-APPA a weak competitive AMPA Receptor antagonist. This observation led us to introduce the new pharmacological concept, functional partial agonism. Recently we have shown that the 2-pyridyl analogue of APPA, (RS)-2-amino-3-[3-hydroxy-5-(2-pyridyl)isoxazol-4-yl]propionic Acid (2-Py-AMPA), is a potent and apparently full AMPA Receptor agonist, and this compound has now been resolved into (+)- and (-)-2-Py-AMPA (ee > or = 99.0%) by chiral HPLC using a Chirobiotic T column. The absolute stereochemistry of the enantiomers of APPA has previously been established by X-ray analysis, and on the basis of comparative studies of the circular dichroism spectra of the enantiomers of APPA and 2-Py-AMPA, (+)- and (-)-2-Py-AMPA were assigned the (S)- and (R)-configuration, respectively. In a series of Receptor binding studies, neither enantiomer of 2-Py-AMPA showed detectable affinity for Kainic Acid Receptor sites or different sites at the N-methyl-D-aspartic Acid (NMDA) Receptor complex. (+)-(S)-2-Py-AMPA was an effective inhibitor of [3H]AMPA binding (IC50 = 0.19 +/- 0.06 microM) and a potent AMPA Receptor agonist in the rat cortical wedge preparation (EC50 = 4.5 +/- 0.3 microM) comparable with AMPA (IC50 = 0.040 +/- 0.01 microM; EC50 = 3.5 +/- 0.2 microM), but much more potent than (+)-(S)-APPA (IC50 = 5.5 +/- 2.2 microM; EC50 = 230 +/- 12 microM). Like (-)-(R)-APPA (IC50 > 100 microM), (-)-(R)-2-Py-AMPA (IC50 > 100 microM) did not significantly affect [3H]AMPA binding, and both compounds were weak AMPA Receptor antagonists (Ki = 270 +/- 50 and 290 +/- 20 microM, respectively).

Tommy N Johansen - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis and Receptor binding affinity of new selective GluR5 ligands.
    Bioorganic & medicinal chemistry, 2001
    Co-Authors: Lennart Bunch, Tine B. Stensbøl, Povl Krogsgaard-larsen, Tommy N Johansen, Hans Bräuner-osborne, Tina H. Johansen, Ulf Madsen
    Abstract:

    Abstract Two hybrid analogues of the Kainic Acid Receptor agonists, 2-amino-3-(5- tert -butyl-3-hydroxy-4-isoxazolyl)propionic Acid (ATPA) and (2 S ,4 R )-4-methylglutamic Acid ((2 S ,4 R )-4-Me-Glu), were designed, synthesized, and characterized in radioligand binding assays using cloned ionotropic and metabotropic glutamic Acid Receptors. The ( S )-enantiomers of E -4-(2,2-dimethylpropylidene)glutamic Acid (( S )- 1 ) and E -4-(3,3-dimethylbutylidene)glutamic Acid (( S )- 2 ) were shown to be selective and high affinity GluR5 ligands, with K i values of 0.024 and 0.39 μM, respectively, compared to K i values at GluR2 of 3.0 and 2.0 μM, respectively. Their affinities in the [ 3 H]AMPA binding assay on native cortical Receptors were shown to correlate with their GluR2 affinity rather than their GluR5 affinity. No affinity for GluR6 was detected (IC 50 >100 μM).

  • Synthesis of deuterium and tritium labelled (RS)-2-Amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)-propionic Acid (ATPA), a selective Kainic Acid Receptor agonist
    Journal of Labelled Compounds and Radiopharmaceuticals, 1999
    Co-Authors: Tommy N Johansen, Tine B. Stensbøl, Bjarke Ebert, Calvin R. Hawes, Gareth J. Ellis, Dorthe Da Graça Thrige, Povl Krogsgaard-larsen
    Abstract:

    (RS)-2-Amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic Acid (ATPA) is an excitatory amino Acid Receptor agonist showing selectivity for the Kainic Acid Receptor subtype GluR5. As part of the pharmacological characterization of GluR5 Receptors, we now report the synthesis of [ 3 H]ATPA based on a four-step synthesis using 5-tert-butyl-3-methoxy-4-isoxazolylcarbaldehyde as the starting material. Using this synthetic procedure deuterium and tritium labelled ATPA have been prepared. [ 3 H]ATPA, with a specific activity of 17 Ci/mmol, was obtained with a radiochemical purity of 98.9%. Attempts to demonstrate specific binding of [ 3 H]ATPA under conventional rat brain membrane Receptor binding conditions were unsuccessful.

  • AMPA Receptor agonists: resolution, configurational assignment, and pharmacology of (+)-(S)- and (-)-(R)-2-amino-3-[3-hydroxy-5-(2-pyridyl)-isoxazol-4-yl]-propionic Acid (2-Py-AMPA).
    Chirality, 1997
    Co-Authors: Tommy N Johansen, Erik Falch, Bjarke Ebert, Povl Krogsgaard-larsen
    Abstract:

    We have previously shown that whereas (RS)-2-amino-3-(3-hydroxy-5-phenylisoxazol-4-yl)propionic Acid (APPA) shows the characteristics of a partial agonist at (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic Acid (AMPA) Receptors, (S)-APPA is a full AMPA Receptor agonist and (R)-APPA a weak competitive AMPA Receptor antagonist. This observation led us to introduce the new pharmacological concept, functional partial agonism. Recently we have shown that the 2-pyridyl analogue of APPA, (RS)-2-amino-3-[3-hydroxy-5-(2-pyridyl)isoxazol-4-yl]propionic Acid (2-Py-AMPA), is a potent and apparently full AMPA Receptor agonist, and this compound has now been resolved into (+)- and (-)-2-Py-AMPA (ee > or = 99.0%) by chiral HPLC using a Chirobiotic T column. The absolute stereochemistry of the enantiomers of APPA has previously been established by X-ray analysis, and on the basis of comparative studies of the circular dichroism spectra of the enantiomers of APPA and 2-Py-AMPA, (+)- and (-)-2-Py-AMPA were assigned the (S)- and (R)-configuration, respectively. In a series of Receptor binding studies, neither enantiomer of 2-Py-AMPA showed detectable affinity for Kainic Acid Receptor sites or different sites at the N-methyl-D-aspartic Acid (NMDA) Receptor complex. (+)-(S)-2-Py-AMPA was an effective inhibitor of [3H]AMPA binding (IC50 = 0.19 +/- 0.06 microM) and a potent AMPA Receptor agonist in the rat cortical wedge preparation (EC50 = 4.5 +/- 0.3 microM) comparable with AMPA (IC50 = 0.040 +/- 0.01 microM; EC50 = 3.5 +/- 0.2 microM), but much more potent than (+)-(S)-APPA (IC50 = 5.5 +/- 2.2 microM; EC50 = 230 +/- 12 microM). Like (-)-(R)-APPA (IC50 > 100 microM), (-)-(R)-2-Py-AMPA (IC50 > 100 microM) did not significantly affect [3H]AMPA binding, and both compounds were weak AMPA Receptor antagonists (Ki = 270 +/- 50 and 290 +/- 20 microM, respectively).

  • AMPA Receptor agonists: resolution, configurational assignment, and pharmacology of (+)-(S)- and (-)-(R)-2-amino-3-[3-hydroxy-5-(2-pyridyl)-isoxazol-4-yl]-propionic Acid (2-Py-AMPA).
    Chirality, 1997
    Co-Authors: Tommy N Johansen, Erik Falch, Bjarke Ebert, Povl Krogsgaard-larsen
    Abstract:

    We have previously shown that whereas (RS)-2-amino-3-(3-hydroxy-5-phenylisoxazol-4-yl)propionic Acid (APPA) shows the characteristics of a partial agonist at (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic Acid (AMPA) Receptors, (S)-APPA is a full AMPA Receptor agonist and (R)-APPA a weak competitive AMPA Receptor antagonist. This observation led us to introduce the new pharmacological concept, functional partial agonism. Recently we have shown that the 2-pyridyl analogue of APPA, (RS)-2-amino-3-[3-hydroxy-5-(2-pyridyl)isoxazol-4-yl]propionic Acid (2-Py-AMPA), is a potent and apparently full AMPA Receptor agonist, and this compound has now been resolved into (+)- and (-)-2-Py-AMPA (ee > or = 99.0%) by chiral HPLC using a Chirobiotic T column. The absolute stereochemistry of the enantiomers of APPA has previously been established by X-ray analysis, and on the basis of comparative studies of the circular dichroism spectra of the enantiomers of APPA and 2-Py-AMPA, (+)- and (-)-2-Py-AMPA were assigned the (S)- and (R)-configuration, respectively. In a series of Receptor binding studies, neither enantiomer of 2-Py-AMPA showed detectable affinity for Kainic Acid Receptor sites or different sites at the N-methyl-D-aspartic Acid (NMDA) Receptor complex. (+)-(S)-2-Py-AMPA was an effective inhibitor of [3H]AMPA binding (IC50 = 0.19 +/- 0.06 microM) and a potent AMPA Receptor agonist in the rat cortical wedge preparation (EC50 = 4.5 +/- 0.3 microM) comparable with AMPA (IC50 = 0.040 +/- 0.01 microM; EC50 = 3.5 +/- 0.2 microM), but much more potent than (+)-(S)-APPA (IC50 = 5.5 +/- 2.2 microM; EC50 = 230 +/- 12 microM). Like (-)-(R)-APPA (IC50 > 100 microM), (-)-(R)-2-Py-AMPA (IC50 > 100 microM) did not significantly affect [3H]AMPA binding, and both compounds were weak AMPA Receptor antagonists (Ki = 270 +/- 50 and 290 +/- 20 microM, respectively).

Derek Bowie - One of the best experts on this subject based on the ideXlab platform.

Birgitte Nielsen - One of the best experts on this subject based on the ideXlab platform.

  • design and synthesis of a series of l trans 4 substituted prolines as selective antagonists for the ionotropic glutamate Receptors including functional and x ray crystallographic studies of new subtype selective Kainic Acid Receptor subtype 1 gluk1 a
    Journal of Medicinal Chemistry, 2017
    Co-Authors: Niels Krogsgaardlarsen, Birgitte Nielsen, Claudia G Delgar, Karina Koch, Patricia M G E Brown, Charlotte Moller, Liwei Han, Tri H V Huynh, Stinne W Hansen, Derek Bowie
    Abstract:

    Ionotropic glutamate Receptor antagonists are valuable tool compounds for studies of neurological pathways in the central nervous system. On the basis of rational ligand design, a new class of selective antagonists, represented by (2S,4R)-4-(2-carboxyphenoxy)pyrrolidine-2-carboxylic Acid (1b), for cloned homomeric Kainic Acid Receptors subtype 1 (GluK1) was attained (Ki = 4 μM). In a functional assay, 1b displayed full antagonist activity with IC50 = 6 ± 2 μM. A crystal structure was obtained of 1b when bound in the ligand binding domain of GluK1. A domain opening of 13–14° was seen compared to the structure with glutamate, consistent with 1b being an antagonist. A structure–activity relationship study showed that the chemical nature of the tethering atom (C, O, or S) linking the pyrrolidine ring and the phenyl ring plays a key role in the Receptor selectivity profile and that substituents on the phenyl ring are well accommodated by the GluK1 Receptor.

  • Design and Synthesis of a Series of l-trans-4-Substituted Prolines as Selective Antagonists for the Ionotropic Glutamate Receptors Including Functional and X‑ray Crystallographic Studies of New Subtype Selective Kainic Acid Receptor Subtype 1 (GluK1)
    2016
    Co-Authors: Niels Krogsgaard-larsen, Birgitte Nielsen, Claudia G Delgar, Karina Koch, Charlotte Moller, Liwei Han, Tri H V Huynh, Stinne W Hansen, Patricia G. E. M. Brown, Derek Bowie
    Abstract:

    Ionotropic glutamate Receptor antagonists are valuable tool compounds for studies of neurological pathways in the central nervous system. On the basis of rational ligand design, a new class of selective antagonists, represented by (2S,4R)-4-(2-carboxyphenoxy)­pyrrolidine-2-carboxylic Acid (1b), for cloned homomeric Kainic Acid Receptors subtype 1 (GluK1) was attained (Ki = 4 μM). In a functional assay, 1b displayed full antagonist activity with IC50 = 6 ± 2 μM. A crystal structure was obtained of 1b when bound in the ligand binding domain of GluK1. A domain opening of 13–14° was seen compared to the structure with glutamate, consistent with 1b being an antagonist. A structure–activity relationship study showed that the chemical nature of the tethering atom (C, O, or S) linking the pyrrolidine ring and the phenyl ring plays a key role in the Receptor selectivity profile and that substituents on the phenyl ring are well accommodated by the GluK1 Receptor

  • Tetrazolyl isoxazole amino Acids as ionotropic glutamate Receptor antagonists: Synthesis, modelling and molecular pharmacology
    Bioorganic & Medicinal Chemistry, 2005
    Co-Authors: Bente Frølund, Tine B. Stensbøl, Ulf Madsen, Mai Marie Holm, Jeremy R. Greenwood, Jan Egebjerg, Hans Bräuner-osborne, Birgitte Nielsen, Povl Krogsgaard-larsen
    Abstract:

    Abstract Two 3-(5-tetrazolylmethoxy) analogues, 1a and 1b , of ( RS )-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic Acid (AMPA), a selective AMPA Receptor agonist, and ( RS )-2-amino-3-(5- tert -butyl-3-hydroxy-4-isoxazolyl)propionic Acid (ATPA), a GluR5-preferring agonist, were synthesized. Compounds 1a and 1b were pharmacologically characterized in Receptor binding assays, and electrophysiologically on homomeric AMPA Receptors (GluR1-4), homomeric (GluR5 and GluR6) and heteromeric (GluR6/KA2) Kainic Acid Receptors, using two-electrode voltage-clamped Xenopus laevis oocytes expressing these Receptors. Both analogues proved to be antagonists at all AMPA Receptor subtypes, showing potencies ( K b  = 38–161 μM) similar to that of the AMPA Receptor antagonist ( RS )-2-amino-3-[3-(carboxymethoxy)-5-methyl-4-isoxazolyl]propionic Acid (AMOA) ( K b  = 43–76 μM). Furthermore, the AMOA analogue, 1a , blocked two Kainic Acid Receptor subtypes (GluR5 and GluR6/KA2), showing sevenfold preference for GluR6/KA2 ( K b  = 19 μM). Unlike the iGluR antagonist ( S )-2-amino-3-[5- tert -butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic Acid [( S )-ATPO], the corresponding tetrazolyl analogue, 1b , lacks Kainic Acid Receptor effects. On the basis of docking to a crystal structure of the isolated extracellular ligand-binding core of the AMPA Receptor subunit GluR2 and a homology model of the Kainic Acid Receptor subunit GluR5, we were able to rationalize the observed structure–activity relationships.

Robert J Delorenzo - One of the best experts on this subject based on the ideXlab platform.

  • epileptogenesis causes an n methyl d aspartate Receptor ca2 dependent decrease in ca2 calmodulin dependent protein kinase ii activity in a hippocampal neuronal culture model of spontaneous recurrent epileptiform discharges
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Abstract Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the hippocampal neuronal culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in hippocampal cultures involves a Ca2+/N-methyl- d -aspartate (NMDA) Receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl -2-amino-5-phosphonovaleric Acid (APV) 25 µM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA)/Kainic Acid Receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA Receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.

  • Epileptogenesis causes an N-methyl-d-aspartate Receptor/Ca2+-dependent decrease in Ca2+/calmodulin-dependent protein kinase II activity in a hippocampal neuronal culture model of spontaneous recurrent epileptiform discharges.
    European Journal of Pharmacology, 2008
    Co-Authors: Robert E Blair, Sompong Sombati, Severn B Churn, Robert J Delorenzo
    Abstract:

    Alterations in the function of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM kinase II has not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long-lasting decrease in CaM kinase II activity in the hippocampal neuronal culture model of low Mg2+-induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in hippocampal cultures involves a Ca2+/N-methyl-d-aspartate (NMDA) Receptor-dependent mechanism. Low Mg2+-induced SREDs result in a significant decrease in Ca2+/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca2+ levels (0.2 mM in treatment solution) or the addition of dl-2-amino-5-phosphonovaleric Acid (APV) 25 microM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA)/Kainic Acid Receptor or L-type voltage sensitive Ca2+ channel had no effect on the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca2+/NMDA Receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.