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Title: Na(+) entry through AMPA receptors results in voltage-gated k(+) channel blockade in cultured rat spinal cord motoneurons
Authors: Van Damme, Philip ×
Van Den Bosch, Ludo
Van Houtte, Elisabeth
Eggermont, Jan
Callewaert, Geert
Robberecht, Wim #
Issue Date: Aug-2002
Series Title: Journal of Neurophysiology vol:88 issue:2 pages:965-72
Abstract: alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor currents, evoked with the agonist kainate, were studied with the gramicidin perforated-patch-clamp technique in cultured rat spinal cord motoneurons. Kainate-induced currents could be blocked by the AMPA receptor antagonist LY 300164 and displayed an apparent strong inward rectification. This inward rectification was not a genuine property of AMPA receptor currents but was a result of a concomitant decrease in outward current at potentials positive to -40.5 +/- 1.3 mV. The AMPA receptor current itself was nearly linear (rectification index 0.91). The kainate-inhibited outward current had a reversal potential close to the estimated K(+) equilibrium potential and was blocked by 30 mM tetraethylammonium. When voltage steps were applied, it was found that kainate inhibited both the delayed rectifier K(+) current K(V) and the transient outward K(+) current, K(A). The kainate-induced inhibition of K(+) currents was dependent on ion flux through the AMPA receptor, because no change in the membrane conductance was noticed in the presence of LY 300164. Removing extracellular Ca(2+) had no effect, whereas replacing extracellular Na(+) or clamping the membrane close to the estimated Na(+) equilibrium potential during kainate application attenuated the inhibition of the K(+) current. Sustained Na(+) influx induced by application of the Na(+) ionophore monensin could mimic the effect of kainate on K(+) conductance. These findings demonstrate that Na(+) influx through AMPA receptors results in blockade of voltage-gated K(+) channels.
URI: 
ISSN: 0022-3077
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Research Group Experimental Neurology
Physiology Section (-)
Laboratory for Neurobiology (Vesalius Research Center)
Laboratory of Cellular Transport Systems
× corresponding author
# (joint) last author

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