Effects Of Lysine Vasopressin Research Articles

Vasopressin-evoked ACTH release in rats following forebrain removal.

SummaryThe effects of lysine vasopressin on plasma concentrations of corticosterone were determined in adult female rats with hypothalamic (HI), pituitary (PI) or anterior pituitary (API) islands. Twenty-four hr after partial brain removal, blood samples were obtained rapidly from the jugular vein for fluorometric determination of “non-stress,”prevasopressin levels of corticosterone. Immediately following sampling, vasopressin (20 mU/100 g of body wt) or saline was injected intravenously; 15 min later rats were decapitated and trunk blood was collected for postvasopressin or -saline corticosterone levels. Whereas HI and PI rats responded to vasopressin with increased plasma corticosterone levels, API and saline-injected HI and PI rats showed no change in corticosterone concentrations. “Nonstress”corticosterone levels were within the physiologic range in HI and PI, but not API rats. These results suggest that the hypothalamus and other forebrain structure are not essential to vasopressin-induced ACTH secre...

The vasopressin test as an aid in the evaluation of hypothalamo-pituitary-adrenal function.

Abstract. The effect of lysine vasopressin (LVP) on plasma 11‐hydroxycorticosteroids (11‐OHCS), when administered intramuscularly at 10 p.m., and at one and two hours later has been studied in a series of 164 individuals, 43 of whom served as controls and the others represented groups of patients with hypopituitarism, glucocorticoid‐treated patients and other metabolically interesting patients. There was a significantly smaller average rise of 11‐OHCS in the hypopituitarism group and in the corticoid‐treated groups than in the control group. Oestrogen‐treated patients responded normally to LVP. The side‐effects caused by the administration of LVP were slight and well tolerated in all patients. In a number of patients the adrenal function was studied with the aid of the 5 hours' intravenous adreno‐corticotropic hormone (ACTH) test after the LVP test. The effect of LVP on the eosinophil cells in the blood was smaller than that caused by ACTH in the i.v. test. The LVP test can be used as a convenient screening test of the hypothalamic‐adrenal system.

THE EFFECT OF LYSINE VASOPRESSIN AND HYPOTHALAMIC EXTRACTS ON THE RATE OF CORTICOSTERONE SECRETION IN RATS TREATED WITH DEXAMETHASONE AND PENTOBARBITONE

SUMMARY The effects of lysine vasopressin (LVP) on the rate of secretion of corticosterone and on its concentration in the peripheral plasma have been compared. A dose of 80 m-u. LVP was required to increase the peripheral plasma concentration of corticosterone, whereas as little as 80 μu. produced a significant increase in the rate of corticosterone secretion. A log—dose response curve has been constructed between 80 and 800 μu. LVP using the secretion rate assay. The effect of hypothalamic extracts on corticosterone secretion in the intact rat was readily detected and a diurnal difference of hypothalamic activity in adrenalectomized rats was found. Extracts of rat cerebral cortex were ineffective in increasing the secretion rate of corticosterone in the dexamethasone—pentobarbitone-treated rat; hypothalamic extracts from intact rats and LVP in doses of 0·1 and 0·8 m-u. showed no corticotrophin(ACTH)-like activity as demonstrated by the measurement of corticosterone secretion in the hypophysectomized rat. Although the measurement of corticosterone secretion in rats pretreated with dexamethasone and pentobarbitone does not fulfil all the criteria for a bioassay for ACTH-releasing factor, it is a very sensitive technique for the detection of the effects of LVP on the activation of the pituitary-adrenal system and can be used to study changes of ACTH-releasing activity in hypothalamic extracts.

Long Term and Short Term Effects on Retention of a Conditioned Avoidance Response in Rats by Treatment with Long Acting Pitressin and α-MSH

ATTENTION has recently been focused on the effect of peptides on conditioned avoidance behaviour. It has been shown that adrenocorticotrophic hormone (ACTH) administered during avoidance learning results in a delay of extinction of a conditioned avoidance response (CAR)1,2. We found that the rapid extinction of a CAR which occurs after posterior lobectomy or hypophysectomy can be prevented by treatment with ACTH, melanocyte stimulating hormone (α-MSH) or lysine vasopressin given during the extinction period3. Our observations indicate that the effect of ACTH which results in a delay of extinction of the CAR is located in the N-terminal part of the peptide, presumably within the first ten amino-acids4,5. The effect of lysine vasopressin or pitressin (posterior pituitary extract) administered during the extinction period appeared to be similar to that of ACTH and related peptides3. Accordingly, it was considered of interest to investigate whether the effect of vasopressin and of an ACTH-like peptide on extinction of the CAR involves the same mechanisms despite the structural difference of these two peptides.