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Mondello SE, Sunshine MD, Fischedick AE, Dreyer SJ, Horwitz GD, Anikeeva P, Horner PJ, Moritz CT. Optogenetic surface stimulation of the rat cervical spinal cord. J Neurophysiol 2018; 120:795-811. [DOI: 10.1152/jn.00461.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Electrical intraspinal microstimulation (ISMS) at various sites along the cervical spinal cord permits forelimb muscle activation, elicits complex limb movements and may enhance functional recovery after spinal cord injury. Here, we explore optogenetic spinal stimulation (OSS) as a less invasive and cell type-specific alternative to ISMS. To map forelimb muscle activation by OSS in rats, adeno-associated viruses (AAV) carrying the blue-light sensitive ion channels channelrhodopsin-2 (ChR2) and Chronos were injected into the cervical spinal cord at different depths and volumes. Following an AAV incubation period of several weeks, OSS-induced forelimb muscle activation and movements were assessed at 16 sites along the dorsal surface of the cervical spinal cord. Three distinct movement types were observed. We find that AAV injection volume and depth can be titrated to achieve OSS-based activation of several movements. Optical stimulation of the spinal cord is thus a promising method for dissecting the function of spinal circuitry and targeting therapies following injury. NEW & NOTEWORTHY Optogenetics in the spinal cord can be used both for therapeutic treatments and to uncover basic mechanisms of spinal cord physiology. For the first time, we describe the methodology and outcomes of optogenetic surface stimulation of the rat spinal cord. Specifically, we describe the evoked responses of forelimbs and address the effects of different adeno-associated virus injection paradigms. Additionally, we are the first to report on the limitations of light penetration through the rat spinal cord.
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Affiliation(s)
- S. E. Mondello
- Department of Rehabilitation Medicine, University of Washington, Seattle, Washington
- Center for Sensorimotor Neural Engineering, Seattle, Washington
| | - M. D. Sunshine
- Department of Rehabilitation Medicine, University of Washington, Seattle, Washington
- Center for Sensorimotor Neural Engineering, Seattle, Washington
| | - A. E. Fischedick
- Department of Rehabilitation Medicine, University of Washington, Seattle, Washington
| | - S. J. Dreyer
- Center for Sensorimotor Neural Engineering, Seattle, Washington
- Department of Bioengineering, University of Illinois, Chicago, Illinois
| | - G. D. Horwitz
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington
- Graduate Program in Neuroscience, University of Washington, Seattle, Washington
- Washington National Primate Research Center, Seattle, Washington
| | - P. Anikeeva
- Center for Sensorimotor Neural Engineering, Seattle, Washington
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - P. J. Horner
- Center for Neuroregeneration, Department of Neurological Surgery, Houston Methodist Research Institute, Houston, Texas
| | - C. T. Moritz
- Department of Rehabilitation Medicine, University of Washington, Seattle, Washington
- University of Washington Institute for Neuroengineering, University of Washington, Seattle, Washington
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington
- Graduate Program in Neuroscience, University of Washington, Seattle, Washington
- Center for Sensorimotor Neural Engineering, Seattle, Washington
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