Vasopressin and A1 noradrenaline turnover during food or water deprivation in the rat

In the present study, we have examined in Wistar rats the effects of food or water deprivation of 3 days on the hypophyso–adrenal axis, vasopressinergic system and activity of A1 noradrenergic brain stem cell group, which is involved in the control of the hypothalamic neuro-endocrine activity. Levels of adrenocorticotropic hormone (ACTH) and vasopressin (AVP) were determined by radio-immunoassay, and corticosterone level was determined by fluorimetric method. Plasma levels of ACTH and corticosterone were greatly increased in both groups of rats. In water-deprived rats, plasma AVP (13.83±1.63 vs. 3.03±0.23 pg/ml) and osmolality levels were significantly elevated with a marked decrease of AVP hypophysis content (272±65 vs. 1098±75 ng/mg protein), but not in food-deprived rats in which osmolality did not change and AVP remained stocked (2082±216 ng/mg protein) in the hypophysis without release in the plasma (1.11±0.23 pg/ml). These observations indicated that both food-deprivation and water-deprivation stimulated the pituitary–adrenal axis thereby suggesting a stress state. AVP production is stimulated both by fluid and food restriction but is secreted with differential effects: during food restriction AVP secretion is limited to supporting the hypothalamic–pituitary–adrenal system.