INCREASED NUMBER OF VASOPRESSIN-EXPRESSING AND OXYTOCIN-EXPRESSING NEURONS IN THE PARAVENTRICULAR NUCLEUS OF THE HYPOTHALAMUS IN DEPRESSION

Background: Cerebrospinal fluid levels of arginine vasopressin (AVP) a nd oxytocin (OXT) have been found to change in mood disorders. In the present study, the numbers of AVP-immunoreactive (IR) and OXT-IR neuro ns were determined in the paraventricular nucleus (PVN) of the human h ypothalamus. Methods: Postmortem brain tissue was fixed in formalin, e mbedded in paraffin, and stained for AVP and OXT using immunocytochemi cal techniques. The number of IR neurons in the PVN was estimated by m orphometry in eight depressed patients ranging in age from 21 to 85 ye ars and eight age-matched controls ranging in age from 23 to 88 years. Results: The numbers of AVP-IR and OXT-IR neurons in the PVN of patie nts with mood disorder were increased by 56% and 23%, respectively. No differences were found in AVP-IR or OXT-IR cell numbers between three patients with major depression and three patients with bipolar depres sion. The numbers of AVP-IR and OXT-IR neurons in two patients with de pression not otherwise specified were within the same range as in the six other patients with a mood disorder. Conclusions: The AVP and OXT neurons were activated in the PVN in patients with major depression or bipolar disorder. This activation may be associated with activation o f the hypothalamic-pituitary-adrenal axis in these patients, since bot h AVP and OXT are known to potentiate the effects of corticotropin-rel easing hormone. Because of their central effects, activation of AVP an d OXT neurons may also be related to symptoms of major depression or b ipolar disorder.