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The Journal of Neuroscience, February 1, 2000, 20(3):1020-1029

A Role for Voltage-Gated Potassium Channels in the Outgrowth of Retinal Axons in the Developing Visual System

Sarah McFarlane and Natashka S. Pollock

University of Calgary, Department of Cell Biology and Anatomy, Calgary, Alberta T2N 4N1, Canada

Neural activity is important for establishing proper connectivity in the developing visual system. Tetrodotoxin blockade of sodium (Na⁺)-dependent action potentials impairs the refining of synaptic connections made by developing retinal ganglion cells (RGCs), but does not affect their ability to get out to their target. Although this may suggest neural activity is not required for the directed extension of RGC axons, in many species developing RGCs express additional, Na⁺-independent ionic mechanisms. To test whether the ability of RGC axons to extend in a directed fashion is influenced by membrane excitability, we blocked the principal modulators of the neural activity of a neuron, voltage-dependent potassium (Kv) channels. First, we showed that RGCs and their growth cones express Kv channels when they are growing through the brain on the way to their main midbrain target, the optic tectum. Second, a Kv channel blocker, 4-aminopyridine (4-AP), was applied to the developing Xenopus optic projection. Blocking Kv channels inhibited RGC axon extension and caused aberrant routing of many RGC fibers. With the higher doses, <25% of embryos had a normal optic projection. These data suggest that Kv channel activity regulates the guidance of growing axons in the vertebrate brain.

Key words: axon guidance; Xenopus; target recognition; growth cone; electrical activity; neurite outgrowth; voltage-dependent potassium channels

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Copyright © 2000 Society for Neuroscience  0270-6474/00/2031020-10$05.00/0

This article has been cited by other articles:

				C. A. Webber, J. C. Hocking, V. W. Yong, C. L. Stange, and S. McFarlane Metalloproteases and Guidance of Retinal Axons in the Developing Visual System J. Neurosci., September 15, 2002; 22(18): 8091 - 8100. [Abstract] [Full Text] [PDF]

				L. Gnuegge, S. Schmid, and S. C. F. Neuhauss Analysis of the Activity-Deprived Zebrafish Mutant macho Reveals an Essential Requirement of Neuronal Activity for the Development of a Fine-Grained Visuotopic Map J. Neurosci., May 15, 2001; 21(10): 3542 - 3548. [Abstract] [Full Text] [PDF]

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