Electroconvulsive shock therapy and maximum binding of platelet tritiated imipramine binding in depression

We studied the tritiated imipramine binding values in platelets from 12 hospitalized untreated patients with endogenous depression and found a significant decrease in maximum binding (Bmax) values compared with a control population of the same age and sex. There were no changes in the equilibrium dissociation affinity constant values between the untreated depressives and the control population. After at least six sessions of electroconvulsive therapy and at the time when a significant clinical improvement of depression was confirmed, the Bmax value of tritiated imipramine binding in platelets was slightly increased but was still significantly below that of the control values. However, when six of these patients were reexamined after 12 to 18 months, at a time when they were euthymic, the Bmax of tritiated imipramine binding in platelets was found in the same range as the values of the control population. Our results indicate that clinical improvement precedes the changes in Bmax of tritiated imipramine binding in platelets from depressed patients. The tritiated imipramine binding in platelets is a useful biologic marker in affective disorders. Furthermore, our results suggest that tritiated imipramine binding in platelets may be a state-dependent biologic marker in depression.