Document Detail

Exercise training after spinal cord injury selectively alters synaptic properties in neurons in adult mouse spinal cord.
MedLine Citation:
PMID:  23320512     Owner:  NLM     Status:  MEDLINE    
Following spinal cord injury (SCI), anatomical changes such as axonal sprouting occur within weeks in the vicinity of the injury. Exercise training enhances axon sprouting; however, the exact mechanisms that mediate exercised-induced plasticity are unknown. We studied the effects of exercise training after SCI on the intrinsic and synaptic properties of spinal neurons in the immediate vicinity (<2 segments) of the SCI. Male mice (C57BL/6, 9-10 weeks old) received a spinal hemisection (T10) and after 1 week of recovery, they were randomized to trained (treadmill exercise for 3 weeks) and untrained (no exercise) groups. After 3 weeks, mice were killed and horizontal spinal cord slices (T6-L1, 250 μm thick) were prepared for visually guided whole cell patch clamp recording. Intrinsic properties, including resting membrane potential, input resistance, rheobase current, action potential (AP) threshold and after-hyperpolarization (AHP) amplitude were similar in neurons from trained and untrained mice (n=67 and 70 neurons, respectively). Neurons could be grouped into four categories based on their AP discharge during depolarizing current injection; the proportions of tonic firing, initial bursting, single spiking, and delayed firing neurons were similar in trained and untrained mice. The properties of spontaneous excitatory synaptic currents (sEPSCs) did not differ in trained and untrained animals. In contrast, evoked excitatory synaptic currents recorded after dorsal column stimulation were markedly increased in trained animals (peak amplitude 78.9±17.5 vs. 42.2±6.8 pA; charge 1054±376 vs. 348±75 pA·ms). These data suggest that 3 weeks of treadmill exercise does not affect the intrinsic properties of spinal neurons after SCI; however, excitatory synaptic drive from dorsal column pathways, such as the corticospinal tract, is enhanced.
Jamie R Flynn; Lynda R Dunn; Mary P Galea; Robin Callister; Robert J Callister; Michelle M Rank
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2013-05-09
Journal Detail:
Title:  Journal of neurotrauma     Volume:  30     ISSN:  1557-9042     ISO Abbreviation:  J. Neurotrauma     Publication Date:  2013 May 
Date Detail:
Created Date:  2013-05-22     Completed Date:  2013-12-23     Revised Date:  2014-05-16    
Medline Journal Info:
Nlm Unique ID:  8811626     Medline TA:  J Neurotrauma     Country:  United States    
Other Details:
Languages:  eng     Pagination:  891-6     Citation Subset:  IM    
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MeSH Terms
Excitatory Postsynaptic Potentials / physiology
Membrane Potentials / physiology
Mice, Inbred C57BL
Neurons / physiology*
Physical Conditioning, Animal / physiology*
Spinal Cord / physiopathology*
Spinal Cord Injuries / physiopathology*
Synapses / physiology*

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