Final answer:
Elevated levels of corticotropin-releasing hormone (CRH), released from the periventricular nucleus of the hypothalamus, are found in depression. CRH stimulates the release of cortisol, contributing to the persistent stress-response system activation associated with major depressive disorder. CRH dysregulation plays a key role in depression pathology.
Step-by-step explanation:
The substance released from the periventricular nucleus of the hypothalamus, which is found at elevated levels in depression, is corticotropin-releasing hormone (CRH). CRH is known to stimulate the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary gland, leading to the secretion of cortisol, a stress hormone, from the adrenal glands. In the case of depression, particularly the melancholic subtype, there is a persistent elevation of cortisol levels alongside increased central CRH, correlating with a state of hyperarousal and anxiety.
Furthermore, studies have demonstrated that chronic activation of the hypothalamic-pituitary-adrenal (HPA) axis associated with elevated CRH is common in major depressive disorder (MDD). While treatments for MDD often target neurotransmitters such as serotonin or norepinephrine, the disruption in CRH levels and the HPA axis is significant in the pathology of depression. Thus, understanding and targeting CRH could be critical for managing certain forms of depression.