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Abnormal axonal physiology is associated with altered expression and distribution of Kv1.1 and Kv1.2 K + channels after chronic spinal cord injury
Author(s) -
Nashmi Raad,
Jones Owen T.,
Fehlings Michael G.
Publication year - 2000
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2000.00926.x
Subject(s) - spinal cord , spinal cord injury , blot , electrophysiology , immunofluorescence , neuroscience , axon , potassium channel , chemistry , cord , medicine , anatomy , biology , biochemistry , immunology , surgery , antibody , gene
Dysfunction of surviving axons which traverse the site of spinal cord injury (SCI) has been linked to altered sensitivity to the K + channel blocker 4‐aminopyridine (4‐AP) and appears to contribute to post‐traumatic neurological deficits although the underlying mechanisms remain unclear. In this study, sucrose gap electrophysiology in isolated dorsal column strips, Western blotting and confocal immunofluorescence microscopy were used to identify the K + channels associated with axonal dysfunction after chronic (6–8 weeks postinjury) clip compresssion SCI of the thoracic cord at T7 in rats. The K + channel blockers 4‐AP (200 μ m , 1 m m and 10 m m ) and α‐dendrotoxin (α‐DTX, 500 n m ) resulted in a significant relative increase in the amplitude and area of compound action potentials (CAP) recorded from chronically injured dorsal column axons in comparison with control noninjured preparations. In contrast, TEA (10 m m ) and CsCl (2 m m ) had similar effects on injured and control spinal cord axons. Western blotting and quantitative immunofluorescence microscopy showed increased expression of Kv1.1 and Kv1.2 K + channel proteins on spinal cord axons following injury. In addition, Kv1.1 and Kv1.2 showed a dispersed staining pattern along injured axons in contrast to a paired juxtaparanodal localization in uninjured spinal cord axons. Furthermore, labelled α‐DTX colocalized with Kv1.1 and Kv1.2 along axons. These findings suggest a novel mechanism of axonal dysfunction after SCI whereby an increased 4‐AP‐ and α‐DTX‐sensitive K + conductance, mediated in part by increased Kv1.1 and Kv1.2 K + channel expression, contributes to abnormal axonal physiology in surviving axons.