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J Neurophysiol. 2015 Sep;114(3):1963-73. doi: 10.1152/jn.00193.2015. Epub 2015 Aug 12.

Potassium currents dynamically set the recruitment and firing properties of F-type motoneurons in neonatal mice.

Author information

1
Centre de Neurophysique, Physiologie et Pathologie, Université Paris Descartes, Centre National de la Recherche Scientifique (UMR 8119), Paris, France felxfel@aol.com.
2
Centre de Neurophysique, Physiologie et Pathologie, Université Paris Descartes, Centre National de la Recherche Scientifique (UMR 8119), Paris, France.

Abstract

In neonatal mice, fast- and slow-type motoneurons display different patterns of discharge. In response to a long liminal current pulse, the discharge is delayed up to several seconds in fast-type motoneurons and their firing frequency accelerates. In contrast, slow-type motoneurons discharge immediately, and their firing frequency decreases at the beginning of the pulse. Here, we identify the ionic currents that underlie the delayed firing of fast-type motoneurons. We find that the firing delay is caused by a combination of an A-like potassium current that transiently suppresses firing on a short time scale and a slowly-inactivating potassium current that inhibits the discharge over a much longer time scale. We then show how these intrinsic currents dynamically shape the discharge threshold and the frequency-input function of fast-type motoneurons. These currents contribute to the orderly recruitment of motoneurons in neonates and might play a role in the postnatal maturation of motor units.

KEYWORDS:

functional properties; potassium currents; spinal motoneurons subtypes

PMID:
26269551
PMCID:
PMC4579294
DOI:
10.1152/jn.00193.2015
[Indexed for MEDLINE]
Free PMC Article

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