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The Journal of Neuroscience, April 2, 2008, 28(14):3824-3834; doi:10.1523/JNEUROSCI.0242-08.2008

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 Previous Article

Development/Plasticity/Repair
Dorsal–Ventral Gradient for Neuronal Plasticity in the Embryonic Spinal Cord

Ricardo H. Pineda and Angeles B. Ribera

Department of Physiology and Biophysics, University of Colorado Denver and Health Sciences Center, Aurora, Colorado 80045

Correspondence should be addressed to Angeles B. Ribera, Department of Physiology and Biophysics, MS 8307, RC-1N, P18-7117, 12800 East 19th Avenue, P.O. Box 6511, Aurora, CO 80045. Email: angie.ribera{at}uchsc.edu

Within the developing Xenopus spinal cord, voltage-gated potassium (Kv) channel genes display different expression patterns, many of which occur in opposing dorsal–ventral gradients. Regional differences in Kv gene expression would predict different patterns of potassium current (I_Kv) regulation. However, during the first 24 h of postmitotic differentiation, all primary spinal neurons undergo a temporally coordinated upregulation of I_Kv density that shortens the duration of the action potential. Here, we tested whether spinal neurons demonstrate regional differences in I_Kv regulation subsequent to action potential maturation. We show that two types of neurons, I and II, can be identified in culture on the basis of biophysical and pharmacological properties of I_Kv and different firing patterns. Chronic increases in extracellular potassium, a signature of high neuronal activity, do not alter excitability properties of either neuron type. However, elevating extracellular potassium acutely after the period of action potential maturation leads to different changes in membrane properties of the two types of neurons. I_Kv of type I neurons gains sensitivity to the blocker XE991, whereas type II neurons increase I_Kv density and fire fewer action potentials. Moreover, by recording from neurons in vivo, we found that primary spinal neurons can be identified as either type I or type II. Type I neurons predominate in dorsal regions, whereas type II neurons localize to ventral regions. The findings reveal a dorsal–ventral gradient for I_Kv regulation and a novel form of neuronal plasticity in spinal cord neurons.

Key words: potassium current; action potential; firing properties; embryo; Xenopus neuron; spinal cord

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Received July 2, 2007; revised March 9, 2008; accepted March 11, 2008.

Correspondence should be addressed to Angeles B. Ribera, Department of Physiology and Biophysics, MS 8307, RC-1N, P18-7117, 12800 East 19th Avenue, P.O. Box 6511, Aurora, CO 80045. Email: angie.ribera{at}uchsc.edu

This article has been cited by other articles:

				R. H. Pineda, C. S. Knoeckel, A. D. Taylor, A. Estrada-Bernal, and A. B. Ribera Kv1 Potassium Channel Complexes In Vivo Require Kv{beta}2 Subunits in Dorsal Spinal Neurons J Neurophysiol, October 1, 2008; 100(4): 2125 - 2136. [Abstract] [Full Text] [PDF]

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