Prolactin and cortisol responses to acute intravenous clomipramine challenge in patients with mania, depression and healthy controls: evidence for reduced serotonergic responsivity

Serotonergic dysregulation has been shown to be involved in the pathophysiology of unipolar and bipolar depression. Neuroendocrine challenge tests have been extensively used to investigate serotonin functioning in the brain. Although the role of serotonin has received a great deal of attention using neuroendocrine challenge paradigms, little effort has been made to explore the role of serotonin in mania. We assessed serotonergic neuroendocrine responsivity in patients with depression (n = 22), mania (n = 11) and 15 healthy controls by measuring the prolactin (PRL) and cortisol responses to i.v. clomipramine (CMI) and searched for possible differences among the groups. Blunted PRL responses to CMI in manic and depressed patients compared to healthy controls were found. The response to CMI disclosed similar results for the 2 patient groups. No significant differences were found among the 3 subject groups in the cortisol response to CMI. The blunted PRL responses to CMI in patients with mania and depression suggest that serotonergic functioning in mania and depression is similarly impaired, at least at the level of hypothalamus-hypophysis.