The Role of Corticotropin-Releasing Factor in the Pathogenesis of Major Depression

It is well established that corticotropin-releasing factor (CRF), a peptide comprised of 41 amino acids, is the major physiological regulator of the pituitary-adrenal axis by virtue of its role as the hypothalamic hypophysiotropic hormone that modulates the secretion of adrenocorticotropin (ACTH) from the anterior pituitary gland. In addition to its neuroendocrine role, CRF appears to function as a neurotransmitter or neuromodulator in extrahypothalamic brain areas. The peptide and its receptors are distributed throughout the central nervous system (CNS), and CRF is released by depolarizing concentrations of potassium in a calcium-dependent manner. After direct CNS administration, CRF produces a number of behavioral and physiological effects that are reminiscent of both an organism's response to stress and to the symptoms of patients with major depression. These include: diminished food consumption, decreased sexual behavior, disturbed sleep, alterations in locomotor activity and sympathetic nervous system activation. Alterations in regional brain CRF concentration in rats were observed after acute and chronic stress, i.e. decreased hypothalamic and increased locus coeruleus CRF concentrations. To test the hypothesis that CRF is hypersecreted in patients with major depression, the concentration of CRF in cerebrospinal fluid (CSF) in drug-free depressed patients and age- and sex-matched controles was measured in two studies. The depressed patients exhibited a clear group-related increase in CSF CRF concentrations. To further test this hypothesis that CRF is chronically hypersecreted in depressed patients, the number and affinity of CRF receptors in frontal cortex was measured in a group of suicides and age-matched controls.(ABSTRACT TRUNCATED AT 250 WORDS)