Daily patterns of serotonin uptake in platelets from psychiatric patients and control volunteers.

Serotonin (5-HT) uptake into platelets from psychiatric patients and controls was measured in the morning and afternoon. Uptake varied with time of day in both groups studied, resulting in four recognizable patterns. Two patterns occurred in the majority of controls. In contrast, uptake patterns in the psychiatric patients were more variable, with each of the four patterns clearly represented. However, except for the fact that uptake was significantly decreased throughout the day in depressed patients, the patterns were not otherwise linked statistically to clinical condition. In any event, the greater variability of daily 5-HT uptake patterns in patients suggests that psychiatric disorders linked presumably to central nervous system (CNS) dysfunction are in some way reflected by labile platelet 5-HT pharmacokinetics.