Gamma-melanotropin response to ovine corticotropin releasing factor in normal humans

Inhibition of the pituitary-adrenal axis with dexamethasone and cortisol in depressed patients and healthy subjects: a dose-response study

Different doses dexamethasone (0.25, 0.5, and 1 mg) or cortisol (30, 60, and 120 mg) were administered PO at 2230h to 39 depressed patients and 20 healthy subjects on nonsuccessive days. The inhibiting capacity of the two steroids on hypothalamo-pituitary axis (HPA) function was evaluated by measuring the plasma levels of cortisol, ACTH, and beta-endorphin at 0900h and 1530h each day following treatment. Baseline levels of the hormones were measured before starting treatment. A dose-dependent suppressive effect of both steroids on the plasma levels of cortisol, ACTH, and beta-endorphin was found both in patients and controls, except for the 0900h levels of cortisol after cortisol treatment. The effects were most profound in the morning. Differences between patients and controls were observed after cortisol treatment, but not dexamethasone, with respect to cortisol, ACTH, and beta-endorphin plasma levels in the morning. Cortisol treatment discriminated dexamethasone nonsuppressors from suppressors (patients and controls) and patients categorized as dexamethasone suppressors from controls in a way that dexamethasone treatment could not. The data favour the idea of impaired corticosteroid feedback beyond the pituitary level as part of HPA dysfunction.

Stimulation of the pituitary-adrenal axis with a low dose [Arg8]-vasopressin in depressed patients and healthy subjects

Graded doses arginine-vasopressin (AVP) were administered to depressed patients and control subjects to compare the sensitivity of the pituitary-adrenal system of these subjects for this compound. The plasma levels of cortisol, adrenocorticotropic hormone (ACTH) and beta-endorphin were measured before and after intravenous AVP injection. The hormonal output was taken as a measure of pituitary-adrenal function. In control subjects 3 doses AVP and placebo were used, whereas in patients two doses AVP, a low and a high dose, and placebo were tested. All tests were carried out in the afternoon when the pituitary-adrenal system is stable and more susceptible for stimulation. Patients were subdivided into dexamethasone suppressors and nonsuppressors based on their DST status before testing to look for differences among these groups. Control subjects showed no response of the hormones to the lowest dose AVP and a moderate response to the higher doses. Interestingly, depressed patients as compared to controls responded more to the lowest dose AVP in particular with respect to ACTH. DST status did not influence the results. These findings suggest an enhanced sensitivity of the pituitary to low doses AVP in depressed patients. Thus, AVP might play a role in HPA dysfunction in depression.

Regional processing of the N- and C-terminal domains of proopiomelanocortin in monkey pituitary and brain

The total content and extent of processing of the gamma 3MSH and beta-endorphin-containing N- and C-terminal domains of proopiomelanocortin were determined in the anterior and intermediate lobes of the pituitaries and in 11 regions of the brains of three Rhesus monkeys. Most immunoreactive gamma 3MSH and beta-endorphin was located in the pituitary lobes, although significant amounts were also found in several brain regions. Sephadex column chromatography revealed that gamma 3MSH immunoreactivity was found primarily as 4K and 9K forms; no gamma 1MSH was detected. beta-Endorphin immunoreactivity was found as beta-endorphin, beta-lipotropin, and as a 5K form which may represent beta-endorphin extended N-terminally by part or all of beta-MSH. In the anterior lobe of the pituitary, the predominant products were 9K gamma 3MSH and beta-lipotropin; in the intermediate lobe, more processed forms (4K gamma 3MSH, beta-endorphin and 5K beta-endorphin) appeared to be preferentially stored. The pattern of processing in various brain regions was similar to that of the intermediate lobe of the pituitary.