3H-P-Aminoclonidine binding to platelets of children & adolescents with major depressive disorder was compared to that of a healthy control population. Significantly higher a2-adrenoceptor Kd & Bmax values were observed in the patient popultation. 3H-Dihydroalprenolol binding to lymphocyte membranes of the same patient population showed significantly higher B-adrenoceptor Bmax values than controls. 3H-Imipramine binding to platelets of these patients showed significantly higher imipramine Kd values in patients with a suicide attempts, whereas the imipramine Bmax values were significantly increased in patients with major depressive disorder with or without a suicide attempt. (31 refs)