Alaproclate effects on voltage-dependent K+ channels and NMDA receptors: Studies in cultured rat hippocampal neurons and fibroblast cells transformed with Kvl.2 K+ channel cDNA

B. E. Svensson, T. R. Werkman, Michael A Rogawski

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Abstract

The effects of alaproclate on voltage-dependent K+ currents and N-methyl-d-aspartate (NMDA) and ψ -aminobutyric acidA (GABAA) receptor currents were investigated in cultured rat hippocampal neurons using whole-cell voltage clamp recording techniques. Alaproclate produced a concentration-dependent block of the sustained voltage-dependent K+ current activated by depolarization from -60 to +40mV (IC50, 6.9μM). At similar concentrations alaproclate also blocked the sustained voltage-dependent K+ current in fibroblast cells transformed to stably express Kvl.2 K+ channels. Analysis of tail currents and the voltage-dependence of the alaproclate block suggested an open-channel blocking mechanism. Alaproclate also produced a potent block of NMDA receptor currents in hippocampal neurons (IC50, 1.1 μM), but did not affect GABAA receptor currents (concentrations up to 100μM). The alaproclate block of NMDA receptors occurred predominantly by an open-channel mechanism, although the drug was also able to block closed NMDA channels at a much slower rate. The interaction of alaproclate with NMDA receptors (activated by 10 μM NMDA) appeared to be governed by a first order binding reaction with forward and reverse rate constants of 6.7 × 103M-1, and 0.025 sec-1, respectively (at -60 mV). At depolarized potentials the alaproclate-induced block of the NMDA receptor current was strongly reduced, a result opposite to that seen with the voltage-activated K+ currents, suggesting that the K+ channel block may occur at a superficial internal site, whereas the NMDA receptor block occurs at a deep external site. ( + )-Alaproclate was a more potent blocker of K+ currents than (-)-alaproclate, whereas a reversed stereoselectivity was observed for NMDA receptor current, supporting the view that alaproclate block of the two channel types occurs at structurally distinct binding sites.

Original languageEnglish (US)
Pages (from-to)795-804
Number of pages10
JournalNeuropharmacology
Volume33
Issue number6
DOIs
StatePublished - 1994
Externally publishedYes

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alaproclate
Complementary DNA
Fibroblasts
Neurons
Aspartic Acid
GABA-A Receptors
Inhibitory Concentration 50
aspartic acid receptor

Keywords

  • alaproclate
  • GABA receptor
  • hippocampus
  • Ion channels
  • K channel
  • NMDA receptor
  • voltage clamp recording
  • voltage-dependent block

ASJC Scopus subject areas

  • Cellular and Molecular Neuroscience
  • Drug Discovery
  • Pharmacology

Cite this

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title = "Alaproclate effects on voltage-dependent K+ channels and NMDA receptors: Studies in cultured rat hippocampal neurons and fibroblast cells transformed with Kvl.2 K+ channel cDNA",
abstract = "The effects of alaproclate on voltage-dependent K+ currents and N-methyl-d-aspartate (NMDA) and ψ -aminobutyric acidA (GABAA) receptor currents were investigated in cultured rat hippocampal neurons using whole-cell voltage clamp recording techniques. Alaproclate produced a concentration-dependent block of the sustained voltage-dependent K+ current activated by depolarization from -60 to +40mV (IC50, 6.9μM). At similar concentrations alaproclate also blocked the sustained voltage-dependent K+ current in fibroblast cells transformed to stably express Kvl.2 K+ channels. Analysis of tail currents and the voltage-dependence of the alaproclate block suggested an open-channel blocking mechanism. Alaproclate also produced a potent block of NMDA receptor currents in hippocampal neurons (IC50, 1.1 μM), but did not affect GABAA receptor currents (concentrations up to 100μM). The alaproclate block of NMDA receptors occurred predominantly by an open-channel mechanism, although the drug was also able to block closed NMDA channels at a much slower rate. The interaction of alaproclate with NMDA receptors (activated by 10 μM NMDA) appeared to be governed by a first order binding reaction with forward and reverse rate constants of 6.7 × 103M-1, and 0.025 sec-1, respectively (at -60 mV). At depolarized potentials the alaproclate-induced block of the NMDA receptor current was strongly reduced, a result opposite to that seen with the voltage-activated K+ currents, suggesting that the K+ channel block may occur at a superficial internal site, whereas the NMDA receptor block occurs at a deep external site. ( + )-Alaproclate was a more potent blocker of K+ currents than (-)-alaproclate, whereas a reversed stereoselectivity was observed for NMDA receptor current, supporting the view that alaproclate block of the two channel types occurs at structurally distinct binding sites.",
keywords = "alaproclate, GABA receptor, hippocampus, Ion channels, K channel, NMDA receptor, voltage clamp recording, voltage-dependent block",
author = "Svensson, {B. E.} and Werkman, {T. R.} and Rogawski, {Michael A}",
year = "1994",
doi = "10.1016/0028-3908(94)90119-8",
language = "English (US)",
volume = "33",
pages = "795--804",
journal = "Neuropharmacology",
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T1 - Alaproclate effects on voltage-dependent K+ channels and NMDA receptors

T2 - Studies in cultured rat hippocampal neurons and fibroblast cells transformed with Kvl.2 K+ channel cDNA

AU - Svensson, B. E.

AU - Werkman, T. R.

AU - Rogawski, Michael A

PY - 1994

Y1 - 1994

N2 - The effects of alaproclate on voltage-dependent K+ currents and N-methyl-d-aspartate (NMDA) and ψ -aminobutyric acidA (GABAA) receptor currents were investigated in cultured rat hippocampal neurons using whole-cell voltage clamp recording techniques. Alaproclate produced a concentration-dependent block of the sustained voltage-dependent K+ current activated by depolarization from -60 to +40mV (IC50, 6.9μM). At similar concentrations alaproclate also blocked the sustained voltage-dependent K+ current in fibroblast cells transformed to stably express Kvl.2 K+ channels. Analysis of tail currents and the voltage-dependence of the alaproclate block suggested an open-channel blocking mechanism. Alaproclate also produced a potent block of NMDA receptor currents in hippocampal neurons (IC50, 1.1 μM), but did not affect GABAA receptor currents (concentrations up to 100μM). The alaproclate block of NMDA receptors occurred predominantly by an open-channel mechanism, although the drug was also able to block closed NMDA channels at a much slower rate. The interaction of alaproclate with NMDA receptors (activated by 10 μM NMDA) appeared to be governed by a first order binding reaction with forward and reverse rate constants of 6.7 × 103M-1, and 0.025 sec-1, respectively (at -60 mV). At depolarized potentials the alaproclate-induced block of the NMDA receptor current was strongly reduced, a result opposite to that seen with the voltage-activated K+ currents, suggesting that the K+ channel block may occur at a superficial internal site, whereas the NMDA receptor block occurs at a deep external site. ( + )-Alaproclate was a more potent blocker of K+ currents than (-)-alaproclate, whereas a reversed stereoselectivity was observed for NMDA receptor current, supporting the view that alaproclate block of the two channel types occurs at structurally distinct binding sites.

AB - The effects of alaproclate on voltage-dependent K+ currents and N-methyl-d-aspartate (NMDA) and ψ -aminobutyric acidA (GABAA) receptor currents were investigated in cultured rat hippocampal neurons using whole-cell voltage clamp recording techniques. Alaproclate produced a concentration-dependent block of the sustained voltage-dependent K+ current activated by depolarization from -60 to +40mV (IC50, 6.9μM). At similar concentrations alaproclate also blocked the sustained voltage-dependent K+ current in fibroblast cells transformed to stably express Kvl.2 K+ channels. Analysis of tail currents and the voltage-dependence of the alaproclate block suggested an open-channel blocking mechanism. Alaproclate also produced a potent block of NMDA receptor currents in hippocampal neurons (IC50, 1.1 μM), but did not affect GABAA receptor currents (concentrations up to 100μM). The alaproclate block of NMDA receptors occurred predominantly by an open-channel mechanism, although the drug was also able to block closed NMDA channels at a much slower rate. The interaction of alaproclate with NMDA receptors (activated by 10 μM NMDA) appeared to be governed by a first order binding reaction with forward and reverse rate constants of 6.7 × 103M-1, and 0.025 sec-1, respectively (at -60 mV). At depolarized potentials the alaproclate-induced block of the NMDA receptor current was strongly reduced, a result opposite to that seen with the voltage-activated K+ currents, suggesting that the K+ channel block may occur at a superficial internal site, whereas the NMDA receptor block occurs at a deep external site. ( + )-Alaproclate was a more potent blocker of K+ currents than (-)-alaproclate, whereas a reversed stereoselectivity was observed for NMDA receptor current, supporting the view that alaproclate block of the two channel types occurs at structurally distinct binding sites.

KW - alaproclate

KW - GABA receptor

KW - hippocampus

KW - Ion channels

KW - K channel

KW - NMDA receptor

KW - voltage clamp recording

KW - voltage-dependent block

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