Effects of electroconvulsive therapy and desipramine on neuroendocrine responses to the clonidine challenge test

To investigate responses to the clonidine challenge test in depression, and after electroconvulsive therapy (ECT) or desipramine treatment for depression, in order to determine the usefulness of noradrenergic responses to clonidine as a state or trait marker in depression.

Twenty-six patients with depression and 15 control subjects.

The psychiatric ward of St. Joseph's Hospital in Hamilton.

In the patients with depression: clonidine challenge pre- and post-treatment with ECT or desipramine. In the controls: 2 clonidine challenge tests 4 to 8 weeks apart.

The primary measure was the growth hormone response to the clonidine challenge. Plasma norepinephrine, 3-methoxy-4-hydroxyphenylglycol (MHPG), cortisol, blood pressure, pulse and sedation levels were examined in subgroups of participants as secondary measures.

The pre-treatment growth hormone response to clonidine was significantly more blunted in patients than in controls (p = 0.02). This response improved in both treatment groups after therapy and, although it remained decreased, there was no longer a significant difference in response between the patients and the controls. In the patients, a decreased growth hormone response to clonidine at baseline was correlated with response to treatment. Of the secondary measures, patient baseline norepinephrine levels were significantly elevated pre- and post-treatment, although there were no significant group-by-time challenge effects. MHPG levels were not significantly different pre- and post-treatment between patients and controls. Baseline blood pressure and pulse were elevated in the patients pre- and post-treatment. These differences were not statistically significant and did not change after treatment. Sedation levels were not significantly different among the groups at baseline. Clonidine-induced sedation occurred significantly earlier in the patients pretreatment and improved to the range of the controls after treatment. Pretreatment cortisol response was significantly more blunted in the patients who received ECT than in the controls; however, the group-by-time effect post-treatment was no longer significant.

Treatment with either desipramine or ECT modified noradrenergic functioning in patients with depression, as assessed by growth hormone response to the clonidine challenge. In the patients, a decreased growth hormone response at baseline was correlated with clinical response. Changes between pre- and post-treatment measures suggest that this challenge test may not be sensitive enough to serve as a trait marker but may correlate with the state of depression in a subpopulation of these patients.