EFFECT OF PREVIOUS ANTIDEPRESSANT THERAPY ON THE GROWTH-HORMONE RESPONSE TO APOMORPHINE

Several lines of evidence suggest a role for dopamine in the pathophys iology of depression. In 1988, we reported a blunted response of growt h hormone (GH) to apomorphine, a dopaminergic agonist, in endogenous d epression. However, an antidepressant washout period is a major confou nding factor in studies assessing the GH response to apomorphine. Inde ed, whereas the influence of tricyclic antidepressants on the GH respo nse to apomorphine is presently unknown, several reports have suggeste d that tricyclics may impair the GH response to clonidine for periods longer than 3 weeks following their discontinuation. In the present st udy, we hypothesized that a blunted GH response to apomorphine in depr essed patients could be related to the recent administration of antide pressants. Therefore, the GH response to apomorphine (0.5 mg) was stud ied in 11 male DSM-III-R major depressive inpatients who had never rec eived antidepressant therapy (group 1) compared to 11 normal controls and 11 major depressive inpatients drug free for at least 2 weeks (gro up 2). The three groups differed significantly in the CH peak response to apomorphine: mean (SD) 5.4 (4.0) ng/ml in group 1, 25.5 (10.7) in normal controls, and 5.5 (5.1) in group 2 (F = 15.5, df = 3, 30, p = 0 .00001). While group 1 and normal controls (F = 21.8, p = 0.0002) as w ell as group 2 and controls (F = 5.6, p = 0.03) differed significantly , group 1 and group 2 did not (F = 0.18, p = 0.68). These results sugg est that a washout period of 2 weeks could be sufficient in studies as sessing the GH response to apomorphine.