Fast kinetics, high-frequency oscillations, and subprimary firing range in adult mouse spinal motoneurons

Marin Manuel*, Caroline Iglesias, Maud Donnet, Félix Leroy, C. J. Heckman, Daniel Zytnicki

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

66 Scopus citations


The fast contraction time of mouse motor units creates a unique situation in which motoneurons have to fire at low frequencies to produce small forces but also at very high frequency (much higher than in cat or rat motoneurons) to reach the fusion frequency of their motor units. To understand how this problem is solved, we performed intracellular recordings of adult mouse spinal motoneurons and investigated systematically their subthreshold properties and their discharge pattern. We show that mouse motoneurons have a much wider range of firing frequencies than cat and rat motoneurons because of three salient features. First, they have a short membrane time constant. This results in a higher cutoff frequency and a higher resonance frequency, which allow mouse motoneurons to integrate inputs at higher frequencies. Second, their afterhyperpolarization (AHP) is faster, allowing the motoneurons to discharge at a higher rate. Third, motoneurons display high-frequency (100-150 Hz) subthreshold oscillations during the interspike intervals. The fast membrane kinetics greatly favors the appearance of these oscillations, creating a "subprimary range" of firing. In this range, which has never been reported in cat and in rat spinal motoneurons, the oscillations follow the AHP and trigger spiking after a variable delay, allowing a discharge at low frequency but at the expense of an irregular rate.

Original languageEnglish (US)
Pages (from-to)11246-11256
Number of pages11
JournalJournal of Neuroscience
Issue number36
StatePublished - Sep 9 2009

ASJC Scopus subject areas

  • General Neuroscience


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