[Functional activity of serotonin- and histaminergic systems in humans during long-term antiorthostatic hypokinesia].

The functional activity of serotonin- and histaminergic systems was investigated during 120-day head-down tilt. Serotonin excretion was increased until test day 70 and histamine excretion throughout the entire study. At the final stage of exposure (test days 100-120) the serotonin content decreased. Return to the normal motor activity stimulated the function of serotonin- and histaminergic systems.