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The Journal of Neuroscience, August 15, 2000, 20(16):6087-6094

Antisense Suppression of Potassium Channel Expression Demonstrates Its Role in Maturation of the Action Potential

Anne Vincent, Nathan J. Lautermilch, and Nicholas C. Spitzer

Department of Biology and Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0357

A developmental increase in delayed rectifier potassium current (I_Kv) in embryonic Xenopus spinal neurons is critical for the maturation of excitability and action potential waveform. Identifying potassium channel genes that generate I_Kv is essential to understanding the mechanisms by which they are controlled. Several Kv genes are upregulated during embryogenesis in parallel with increases in I_Kv and produce delayed rectifier current when heterologously expressed, indicating that they could encode channels underlying this current. We used antisense (AS) cRNA to test the contribution of xKv3.1 to the maturation of I_Kv, because xKv3.1 AS appears to suppress specifically heterologous expression of potassium current by xKv3.1 mRNA. The injection of xKv3.1 AS into embryos reduces endogenous levels of xKv3.1 mRNA in the developing spinal cord and reduces the amplitude and rate of activation of I_Kv in 40% of cultured neurons, similar to the percentage of neurons in which endogenous xKv3.1 transcripts are detected. The current in these mature neurons resembles that at an earlier stage of differentiation before the appearance of xKv3.1 mRNA. Furthermore, AS expression increases the duration of the action potential in 40% of the neurons. No change in voltage-dependent calcium current is observed, suggesting that the decrease in I_Kv is sufficient to account for lengthening of the action potential. Computer-simulated action potentials incorporating observed reductions in amplitude and rate of activation of I_Kv exhibit an increase in duration similar to that observed experimentally. Thus xKv3.1 contributes to the maturation of I_Kv in a substantial percentage of these developing spinal neurons.

Key words: maturation of excitability; delayed rectifier current; Kv3.1; antisense suppression; neuronal differentiation; spinal cord neurons; Xenopus embryos

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Copyright © 2000 Society for Neuroscience  0270-6474/00/20166087-08$05.00/0

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