title: High-frequency transcutaneous electrical nerve stimulation alleviates spasticity after spinal contusion by inhibiting activated microglia in rats.
abstract: BACKGROUND
  Transcutaneous electrical nerve stimulation (TENS) can be used as a physical therapy for spasticity, but the effects of TENS on spasticity and its underlying mechanisms remain unclear.
  
  
  OBJECTIVE
  The purpose of this study was to test the effects of TENS on spasticity and the role of activated microglia as underlying mechanisms of TENS treatment for spasticity in rats with a 50-mm contusive spinal cord injury (SCI).
  
  
  METHODS
  A spinal contusion was made at the T12 spinal segment in adult male Sprague-Dawley rats using the NYU impactor. Behavioral tests for motor function were conducted before and after SCI and before and after TENS application. To assess spasticity, the modified Ashworth scale (MAS) was used before and after SCI, high-frequency (HF)/low-frequency (LF) TENS application at 3 different intensities (motor threshold [MT], 50% and 90% MT) or minocycline administration. Immunohistochemistry for microglia was performed at the lumbar spinal segments.
  
  
  RESULTS
  Motor recovery reached a plateau approximately 28 days after SCI. Spasticity was well developed and was sustained above the MAS grade of 3, beginning at 28 days after SCI. HF-TENS at 90% MT significantly alleviated spasticity. Motor function did not show any significant changes with LF- or HF-TENS treatment. HF-TENS significantly reduced the proportion of activated microglia observed after SCI. Minocycline, the microglia inhibitor, also significantly alleviated spasticity with the reduction of activated microglia expression.
  
  
  CONCLUSIONS
  These results suggest that HF-TENS at 90% MT alleviates spasticity in rats with SCI by inhibiting activated microglia.
authors.affiliation: Department of Physical Therapy, Korea University College of Health Science, Seoul, Korea Rehabilitation Science Program, Department of Health Science, Graduate School, Korea University, Seoul, Korea BK21+ Program in Embodiment, Health-Society Interaction, Department of Public Health Science, Graduate School, Korea University, Seoul, Korea.
authors.forename: Suk-Chan
authors.initials: SC
authors.lastname: Hahm
authors.affiliation: Neuroscience Research Institute and Department of Physiology, Korea University College of Medicine, Seoul, Korea.
authors.forename: Young Wook
authors.initials: YW
authors.lastname: Yoon
authors.affiliation: Department of Physical Therapy, Korea University College of Health Science, Seoul, Korea Rehabilitation Science Program, Department of Health Science, Graduate School, Korea University, Seoul, Korea BK21+ Program in Embodiment, Health-Society Interaction, Department of Public Health Science, Graduate School, Korea University, Seoul, Korea junokim@korea.ac.kr.
authors.forename: Junesun
authors.initials: J
authors.lastname: Kim
mesh_terms: D000818:Animals; D008297:Male; D017628:Microglia / Q000378:metabolism*; D009128:Muscle Spasticity / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013119:Spinal Cord Injuries / Q000150:complications / Q000503:physiopathology*; D013904:Thoracic Vertebrae; D004561:Transcutaneous Electric Nerve Stimulation
keywords: microglia; spasticity; spinal cord injury; transcutaneous electrical nerve stimulation (TENS)