Imipramine binding sites on platelets of patients with major depressive disorder.

3H-Imipramine binding to platelets of patients with primary, unipolar major depressive disorder was investigated and compared to that of a normal, healthy control population. No significant differences could be demonstrated between either the Kd or the Bmax values of the two groups. A negative correlation was observed between imipramine Bmax values and the Hamilton anxiety ratings of the depressed patients. Patients who displayed psychomotor retardation tended to have lower platelet imipramine Bmax values than patients with psychomotor agitation. It is suggested that platelet imipramine Bmax values may be a biological marker for subtypes of depression.