High-affinity 3H-imipramine binding in platelets from untreated and treated depressed patients compared to healthy volunteers.

Specific high-affinity binding of 3H-imipramine to human platelets possesses very similar characteristics to the sites previously described in animal and human brains. In a study comparing the binding of 3H-imipramine in platelets obtained from 39 control volunteers with 37 hospitalized, untreated, severely depressed patients, the maximal binding of 3H-imipramine was found to be significantly lower in the depressed population. There were no differences in the KD values. After 7-15 days of treatment with tricyclic anti-depressant drugs, there was an improvement in the degree of the depression but no significant change in the maximal 3H-imipramine binding. After an average of 50 days treatment, Hamilton ratings had returned to normal, but the 3H-imipramine binding values remained unchanged.