title: Increased urinary excretion rates of serotonin and metabolites during bedrest.
abstract: 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.
authors.affiliation: Institute of Cardiology and Sports Medicine, German Sports University, Cologne, Germany. platen@dshs-koeln.de
authors.forename: Petra
authors.initials: P
authors.lastname: Platen
authors.forename: Marion
authors.initials: M
authors.lastname: Lebenstedt
authors.forename: Myriam
authors.initials: M
authors.lastname: Schneider
authors.forename: Andrea
authors.initials: A
authors.lastname: Boese
authors.forename: Martina
authors.initials: M
authors.lastname: Heer
mesh_terms: 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
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid