Increased urinary excretion rates of serotonin and metabolites during bedrest.
Astronauts are often on a voluntarily reduced energy intake during space missions, possibly caused by a metabolic or emotional stress response with involvement of the central serotonergic system (SES). We investigated 24 h urinary excretion (24 h-E) of serotonin (5-HT) and 5-hydroxyindol acidic acid as indicators of the SES in healthy males under two different normocaloric conditions: normal physical activity (NPA) and -6 degree head-down-tilt (HDT). HDT or NPA were randomly arranged with a recovery period of 6 months in between. 24 h-E of hormones varied widely among individuals. Values were higher in HDT compared to NPA. Assuming that the 24 h-E values are, beside being indicators for alterations in the number and metabolism of platelets. Also indicators of central SES, HDT condition seems to activate central SES in a higher degree compared to NPA. Therefore, changes in central SES might be involved in the mechanisms associated with space flight or microgravity, including possible maladaptations such as voluntary undernutrition.
Platen
Petra
P
Institute of Cardiology and Sports Medicine, German Sports University, Cologne, Germany. platen@dshs-koeln.de
Lebenstedt
Marion
M
Schneider
Myriam
M
Boese
Andrea
A
Heer
Martina
M
D000222:Adaptation, Physiological; D000328:Adult; D001510:Bed Rest; D001835:Body Weight; D002149:Energy Intake; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D018475:Head-Down Tilt; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000652:urine*; D008297:Male; D012701:Serotonin / Q000652:urine*; D018474:Weightlessness Simulation
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid