Seasonal serotonin uptake changes in healthy subjects

Platelet 5-hydroxytryptamine (5HT) uptake was measured in 12 healthy subjects in the spring, summer, and late autumn. The uptake was performed according to the method of Arora and Meltzer (1981). The maximal velocity of 5HT uptake was higher in the spring and in summer than in the autumn. In addition, a significant negative correlation between the Michaelis constant and the photoperiod was observed in spring. These findings seem to indicate the possible evidence of physiological season-related changes of platelet 5HT uptake that may be linked to the photoperiod.