title: Effects of Head-down Tilt on Nerve Conduction in Rhesus Monkeys.
abstract: BACKGROUND
  Few studies have focused on peripheral nerve conduction during exposure to microgravity. The -6° head-down tilt (HDT) comprises an experimental model used to simulate the space flight environment. This study investigated nerve conduction characteristics of rhesus monkeys before and after prolonged exposure to HDT.
  
  
  METHODS
  Six rhesus monkeys (3-4 years old) were tilted backward 6° from the horizontal. Nerve conduction studies (NCSs) were performed on the median, ulnar, tibial, and fibular motor nerves. Analysis of variance with a randomized block design was conducted to compare the differences in the NCS before and 7, 21, and 42 days after the -6° HDT.
  
  
  RESULTS
  The proximal amplitude of the CMAP of the median nerve was significantly decreased at 21 and 42 days of HDT compared with the amplitude before HDT (4.38 ± 2.83 vs. 8.40 ± 2.66 mV, F = 4.85, P = 0.013 and 3.30 ± 2.70 vs. 8.40 ± 2.66 mV, F = 5.93, P = 0.004, respectively). The distal amplitude of the CMAP of the median nerve was significantly decreased at 7, 21, and 42 days of HDT compared with the amplitude before HDT (7.28 ± 1.27 vs. 10.25 ± 3.40 mV, F = 4.03, P = 0.039; 5.05 ± 2.01 vs. 10.25 ± 3.40 mV, F = 6.25, P = 0.04; and 3.95 ± 2.79 vs. 10.25 ± 3.40 mV, F = 7.35, P = 0.01; respectively). The proximal amplitude of the CMAP of the tibial nerve was significantly decreased at 42 days of HDT compared with the amplitude before HDT (6.14 ± 1.94 vs. 11.87 ± 3.19 mV, F = 5.02, P = 0.039).
  
  
  CONCLUSIONS
  This study demonstrates that the compound muscle action potential amplitudes of nerves are decreased under simulated microgravity in rhesus monkeys. Moreover, rhesus monkeys exposed to HDT might be served as an experimental model for the study of NCS under microgravity.
authors.affiliation: Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Sun
authors.affiliation: Department of Neurology, 306th Hospital of People's Liberation Army, Beijing 100101, China.
authors.forename: Xiao-Yun
authors.initials: XY
authors.lastname: Zhang
authors.affiliation: Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, China.
authors.forename: Li-Zhi
authors.initials: LZ
authors.lastname: Liu
authors.affiliation: Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, China.
authors.forename: Zhao-Hui
authors.initials: ZH
authors.lastname: Chen
authors.affiliation: Department of Biomedical Engineering, Astronaut Research and Training Center, Beijing 100101, China.
authors.forename: Zhong-Quan
authors.initials: ZQ
authors.lastname: Dai
authors.affiliation: Department of Neurology, Chinese People's Liberation Army General Hospital, Beijing 100853, China.
authors.forename: Xu-Sheng
authors.initials: XS
authors.lastname: Huang
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D005260:Female; D018475:Head-Down Tilt / Q000502:physiology*; D008253:Macaca mulatta; D008297:Male; D009431:Neural Conduction / Q000502:physiology*; D018474:Weightlessness Simulation