HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free APPENDIX A All Versions of this Article: 101/4/1228    most recent 00482.2006v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Gardiner, P. Articles by Heckman, C. J. Search for Related Content PubMed PubMed Citation Articles by Gardiner, P. Articles by Heckman, C. J.

INVITED REVIEW

HIGHLIGHTED TOPIC
Neural Changes Associated with Training

Effects of exercise training on -motoneurons

¹Spinal Cord Research Center, Department of Physiology, and ²Health, Leisure and Human Performance Research Institute, University of Manitoba, Winnipeg, Manitoba, Canada; and ³Departments of Physiology and Physical Medicine and Rehabilitation, Northwestern University, Evanston, Illinois

Evidence is presented that one locus of adaptation in the "neural adaptations to training" is at the level of the -motoneurons. With increased voluntary activity, these neurons show evidence of dendrite restructuring, increased protein synthesis, increased axon transport of proteins, enhanced neuromuscular transmission dynamics, and changes in electrophysiological properties. The latter include hyperpolarization of the resting membrane potential and voltage threshold, increased rate of action potential development, and increased amplitude of the afterhyperpolarization following the action potential. Many of these changes demonstrate intensity-related adaptations and are in the opposite direction under conditions in which chronic activity is reduced. A five-compartment model of rat motoneurons that innervate fast and slow muscle fibers (termed "fast" and "slow" motoneurons in this paper), including 10 active ion conductances, was used to attempt to reproduce exercise training-induced adaptations in electrophysiological properties. The results suggest that adaptations in -motoneurons with exercise training may involve alterations in ion conductances, which may, in turn, include changes in the gene expression of the ion channel subunits, which underlie these conductances. Interestingly, the acute neuromodulatory effects of monoamines on motoneuron properties, which would be a factor during acute exercise as these monoaminergic systems are activated, appear to be in the opposite direction to changes measured in endurance-trained motoneurons that are at rest. It may be that regular increases in motoneuronal excitability during exercise via these monoaminergic systems in fact render the motoneurons less excitable when at rest. More research is required to establish the relationships between exercise training, resting and exercise motoneuron excitability, ion channel modulation, and the effects of neuromodulators.

spinal cord; modeling; neuromodulation; electrophysiology

This article has been cited by other articles:

				K. Ng, J. Howells, J. D. Pollard, and D. Burke Up-regulation of slow K+ channels in peripheral motor axons: a transcriptional channelopathy in multiple sclerosis Brain, August 12, 2008; (2008) awn180v1. [Abstract] [Full Text] [PDF]

				C. J. Heckman, A. S. Hyngstrom, and M. D. Johnson Active properties of motoneurone dendrites: diffuse descending neuromodulation, focused local inhibition J. Physiol., March 1, 2008; 586(5): 1225 - 1231. [Abstract] [Full Text] [PDF]

				S. K. Jankelowitz, J. Howells, and D. Burke Plasticity of inwardly rectifying conductances following a corticospinal lesion in human subjects J. Physiol., June 15, 2007; 581(3): 927 - 940. [Abstract] [Full Text] [PDF]

				E. P. Zehr Training-induced adaptive plasticity in human somatosensory reflex pathways J Appl Physiol, December 1, 2006; 101(6): 1783 - 1794. [Abstract] [Full Text] [PDF]