title: [Effects of simulated microgravity on the contents of monoamine transmitters in human plasma during heat stress].
abstract: OBJECTIVE
  Using high performance liquid chromatography-electrochemistry detection method to study the effects of simulated microgravity of a 7-day bed-rest in - 6 degrees head-down title (HDT) position, heat stress and their combination on the contents of monoamine transmitters in human plasma, the aim of the present study is to examine effects of simulated microgravity on the contents of monoamine transmitters during heat stress and to investigate the mechanism of human responses to heat stress in spaceflight.
  
  
  RESULTS
  (1) The content of 5-HT, NE, E did not change significantly (P > 0.05) after simulated microgravity alone. (2) Exposed to heat stress alone, the content of 5-HT produced a marked decrease (P < 0.01) at > 40 degrees C, while the contents of NE, E had manifested increases (P < 0.01) at > or = 50 degrees C. (3) Under the effect of the combination of simulated microgravity and heat stress, compared with control group, there was a significant decrease in the content of 5-HT (P < 0.01), but NE, E did not change significantly (P > 0.05). Compared with heat stress alone, there was a significant decrease in the content of NE, E (P < 0.001), while 5-HT did not change significantly (P > 0.05).
  
  
  CONCLUSIONS
  Simulated microgravity decreased the content of heat-induced NE, E, significantly, and the suppression probably plays an important role in degraded human response to heat stress in spaceflight.
authors.affiliation: Institute of Space Medico-Engineering, Beijing 100094, China.
authors.forename: X P
authors.initials: XP
authors.lastname: Chen
authors.forename: X J
authors.initials: XJ
authors.lastname: Yu
authors.forename: S Y
authors.initials: SY
authors.lastname: Chang
authors.forename: J X
authors.initials: JX
authors.lastname: Fei
mesh_terms: D000328:Adult; D015306:Biogenic Monoamines / Q000097:blood*; D018475:Head-Down Tilt; D018882:Heat Stress Disorders / Q000097:blood*; D006801:Humans; D008297:Male; D018474:Weightlessness Simulation
chemical_list: D015306:Biogenic Monoamines