Seasonal variation of platelet serotonin uptake and 3H-imipramine binding in normal and depressed subjects

A striking seasonal variation of 3H-imipramine binding sites and serotonin uptake in blood platelets is demonstrated in normal controls and depressed patients, with lower values in winter and spring than in summer and fall.

Abstract

Density of 3H-imipramine binding sites and serotonin (5-HT) uptake in blood platelets were repeatedly recorded in normal controls (n = 9) and depressed patients (n = 7 for the imipramine binding assay and n = 4 for the serotonin uptake) over a 1-year period. The study demonstrated a striking seasonal variation of both parameters in both groups, with lower values in winter and spring than in summer and fall. No difference in the density of 3H-imipramine binding sites was found between the two populations throughout the year, but serotonin uptake was significantly decreased in depressed patients in May and September. These results underscore the importance of studying controls and patients at the same time of the year.