Platelet [3H]imipramine binding in depressed patients and its circadian variations in healthy controls.

Platelet [3H]imipramine binding was determined in 28 patients with major depression, 11 with bipolar disorders, and 28 healthy controls. The mean maximum number of binding sites (Bmax) in depressed patients was significantly lower than in healthy controls. A significant negative correlation was found between the Bmax values and the total scores of the 17-item Hamilton depression rating scale in major depression. Our results suggest that the Bmax values in major depression may be related to severity of depression. There were significant circadian variations in the Bmax values of [3H]imipramine binding on human platelets from six healthy controls. The mean Bmax values were significantly low in the dark phase and high in the light phase.