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Voltage‐gated potassium channels regulate the response of retinal growth cones to axon extension and guidance cues
Author(s) -
Pollock N. S.,
AtkinsonLeadbeater K.,
Johnston J.,
Larouche M.,
Wildering W. C.,
McFarlane S.
Publication year - 2005
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 - 10.1111/j.1460-9568.2005.04242.x
Subject(s) - tetraethylammonium , microbiology and biotechnology , neuroscience , growth cone , retinal ganglion cell , biology , retina , retinal , dorsal root ganglion , chemistry , axon , biophysics , anatomy , biochemistry , potassium , spinal cord , organic chemistry
Xenopus retinal ganglion cell growth cones express various voltage‐gated potassium (Kv) channels. We showed previously that 4‐aminopyridine and tetraethylammonium have different effects on the outward currents of embryonic Xenopus retinal ganglion cells. Therefore, we asked whether these Kv channel inhibitors differentially regulate the response of retinal ganglion cell growth cones to extrinsic cues. First, we tested the role of Kv channels in axon extension mediated by a substrate bound cue and found that 4‐aminopyridine blocked, whereas tetraethylammonium enhanced basal extension on laminin. Yet, when the growth cones were stimulated to extend with application of soluble growth factors, both inhibitors resulted in a return to the basal extension rates observed in the presence of laminin alone. Second, we asked if Kv channels modulate the response of retinal ganglion cell growth cones to a guidance cue, the chemorepellent fibroblast growth factor‐2. When presented in a gradient to one side of the growth cone, fibroblast growth factor‐2 repulsed retinal ganglion cell growth cones in the presence of 4‐aminopyridine but not tetraethylammonium. These data argue that tetraethylammonium‐ and 4‐aminopyridine‐sensitive Kv channels differ in the manner by which they regulate the response of retinal ganglion cell axons to extension and guidance cues. Non‐ratiometric calcium imaging indicated that differences in the ability of tetraethylammonium‐ and 4‐aminopyridine‐sensitive Kv channels to regulate calcium activity within the growth cone may underlie their unique modulation of growth cone behaviour.