Iglesias, Caroline, Meunier, C., Manuel, M., Timofeeva, Yulia, Delestree, N. and Zytnicki, D.. (2011) Mixed mode oscillations in mouse spinal motoneurons arise from a low excitability state. Journal of Neuroscience, Vol.31 (No.15). pp. 5829-5840. ISSN 0270-6474

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Abstract

We explain the mechanism that elicits the mixed mode oscillations (MMOs) and the subprimary firing range that we recently discovered in mouse spinal motoneurons. In this firing regime, high-frequency subthreshold oscillations appear a few millivolts below the spike voltage threshold and precede the firing of a full blown spike. By combining intracellular recordings in vivo (including dynamic clamp experiments) in mouse spinal motoneurons and modeling, we show that the subthreshold oscillations are due to the spike currents and that MMOs appear each time the membrane is in a low excitability state. Slow kinetic processes largely contribute to this low excitability. The clockwise hysteresis in the I–F relationship, frequently observed in mouse motoneurons, is mainly due to a substantial slow inactivation of the sodium current. As a consequence, less sodium current is available for spiking. This explains why a large subprimary range with numerous oscillations is present in motoneurons displaying a clockwise hysteresis. In motoneurons whose I–F curve exhibits a counterclockwise hysteresis, it is likely that the slow inactivation operates on a shorter time scale and is substantially reduced by the de-inactivating effect of the afterhyperpolarization (AHP) current, thus resulting in a more excitable state. This accounts for the short subprimary firing range with only a few MMOs seen in these motoneurons. Our study reveals a new role for the AHP current that sets the membrane excitability level by counteracting the slow inactivation of the sodium current and allows or precludes the appearance of MMOs.

Item Type:	Journal Article
Subjects:	Q Science > QA Mathematics Q Science > QH Natural history > QH301 Biology Q Science > QP Physiology R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
Divisions:	Faculty of Science > Centre for Complexity Science Faculty of Science > Computer Science
Library of Congress Subject Headings (LCSH):	Motor neurons, Computational neuroscience, Oscillations -- Experiments, Spinal cord -- Experiments, Excitation (Physiology), Mice -- Experiments, Anesthetics -- Physiological effect
Journal or Publication Title:	Journal of Neuroscience
Publisher:	Informa Healthcare
ISSN:	0270-6474
Date:	April 2011
Volume:	Vol.31
Number:	No.15
Page Range:	pp. 5829-5840
Identification Number:	10.1523/JNEUROSCI.6363-10.2011
Status:	Peer Reviewed
Publication Status:	Published
Funder:	Association Française Contre les Myopathies, Centre national de la recherche scientifique (France) (CNRS)
Grant number:	14229 (AFM)
URI:	http://wrap.warwick.ac.uk/id/eprint/36441

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