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Muscle length-dependent contribution of motoneuron Ca(v)1.3 channels to force production in model slow motor unit

Title
Muscle length-dependent contribution of motoneuron Ca(v)1.3 channels to force production in model slow motor unit
Authors
Kim, Hojeong
DGIST Authors
Kim, Hojeong
Issue Date
2017-07
Citation
Journal of Applied Physiology, 123(1), 88-105
Type
Article
Article Type
Article
Keywords
Alpha MotoneuronsCat Soleus MuscleDendritic ExcitabilityDendritic ExcitabilityDynamic ModelForce PotentiationForce PotentiationFrog Skeletal MuscleIn VivoL Type Ca ChannelMedial GastrocnemiusMotor UnitMotor UnitPersistent Inward CurrentsPlateau Like BehaviorSpinal MotoneuronSpinal MotoneuronSpinal MotoneuronsSystematic Variations
ISSN
8750-7587
Abstract
Persistent inward current (PIC)- generating Cav1.3 channels in spinal motoneuron dendrites are thought to be actively recruited during normal behaviors. However, whether and how the activation of PIC channels influences force output of motor unit remains elusive. Here, building a physiologically realistic model of slow motor unit I demonstrated that force production induced by the PIC activation is much smaller for short than lengthened muscles during the regular firing of the motoneuron that transitions from the quiescent state by either a brief current pulse at the soma or a brief synaptic excitation at the dendrites. By contrast, the PIC-induced force potentiation was maximal for short muscles when the motoneuron switched from a stable low-frequency firing state to a stable high-frequency firing state by the current pulse at the soma. Under the synaptic excitation at the dendrites, however, the force could not be potentiated by the transitioning of the motoneuron from a low- to a high-frequency firing state due to the simultaneous onset of PIC at the dendrites and firing at the soma. The strong dependency of the input-output relationship of the motor unit on the neuromodulation and Ia afferent inputs for the PIC channels was further shown under static variations in muscle length. Taken together, these findings suggest that the PIC activation in the motoneuron dendrites may differentially affect the force production of the motor unit, depending not only on the firing state history of the motoneuron and the variation in muscle length but also on the mode of motor activity. NEW & NOTEWORTHY Cav1.3 channels in motoneuron dendrites are actively involved during normal motor activities. To investigate the effects of the activation of motoneuron Cav1.3 channels on force production, a model motor unit was built based on best-available data. The simulation results suggest that force potentiation induced by Cav1.3 channel activation is strongly modulated not only by firing history of the motoneuron but also by length variation of the muscle as well as neuromodulation inputs from the brainstem. Copyright © 2017 the American Physiological Society.
URI
http://hdl.handle.net/20.500.11750/4140
DOI
10.1152/japplphysiol.00491.2016
Publisher
American Physiological Society
Related Researcher
Files:
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Collection:
Companion Diagnostics and Medical Technology Research Group1. Journal Articles


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