Longitudinal optogenetic motor mapping revealed structural and functional impairments and enhanced corticorubral projection after contusive spinal cord injury in Mice

Jun Qian, Wei Wu, Wenhui Xiong, Zhi Chai, Xiao-Ming Xu, Xiaoming Jin

Research output: Contribution to journalArticle

Abstract

Current evaluation of impairment and repair after spinal cord injury (SCI) is largely dependent on behavioral assessment and histological analysis of injured tissue and pathways. Here, we evaluated whether transcranial optogenetic mapping of motor cortex could reflect longitudinal structural and functional damage and recovery after SCI. In Thy1-Channelrhodopsin2 transgenic mice, repeated motor mappings were made by recording optogenetically evoked electromyograms (EMGs) of a hindlimb at baseline and 1 day and 2, 4, and 6 weeks after mild, moderate, and severe spinal cord contusion. Injuries caused initial decreases in EMG amplitude, losses of motor map, and subsequent partial recoveries, all of which corresponded to injury severity. Reductions in map size were positively correlated with motor performance, as measured by Basso Mouse Scale, rota-rod, and grid walk tests, at different time points, as well as with lesion area at spinal cord epicenter at 6 weeks post-SCI. Retrograde tracing with Fluoro-Gold showed decreased numbers of cortico- and rubrospinal neurons, with the latter being negatively correlated with motor map size. Combined retro- and anterograde tracing and immunostaining revealed more neurons activated in red nucleus by cortical stimulation and enhanced corticorubral axons and synapses in red nucleus after SCI. Electrophysiological recordings showed lower threshold and higher amplitude of corticorubral synaptic response after SCI. We conclude that transcranial optogenetic motor mapping is sensitive and efficient for longitudinal evaluation of impairment and plasticity of SCI, and that spinal cord contusion induces stronger anatomical and functional corticorubral connection that may contribute to spontaneous recovery of motor function.

Original languageEnglish (US)
Pages (from-to)485-499
Number of pages15
JournalJournal of Neurotrauma
Volume36
Issue number3
DOIs
StatePublished - Feb 1 2019

Fingerprint

Optogenetics
Spinal Cord Injuries
Red Nucleus
Electromyography
Neurons
Recovery of Function
Wounds and Injuries
Motor Cortex
Hindlimb
Synapses
Transgenic Mice
Axons
Spinal Cord

Keywords

  • corticorubral pathway
  • corticospinal tract
  • motor mapping
  • optogenetics
  • spinal cord injury

ASJC Scopus subject areas

  • Clinical Neurology

Cite this

Longitudinal optogenetic motor mapping revealed structural and functional impairments and enhanced corticorubral projection after contusive spinal cord injury in Mice. / Qian, Jun; Wu, Wei; Xiong, Wenhui; Chai, Zhi; Xu, Xiao-Ming; Jin, Xiaoming.

In: Journal of Neurotrauma, Vol. 36, No. 3, 01.02.2019, p. 485-499.

Research output: Contribution to journalArticle

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