Abstract
Stress adaptation is fundamental for health, and the hypothalamic-pituitary-adrenal axis (HPA) is one of its main mechanisms. Considerable data indicate that arginine vasopressin (AVP) related disturbances of stress adaptation can occur with aging. However, most studies of such kind have been performed on rodents, give contradictory results and fail to consider individual characteristics of the animals. The purpose of this study was to investigate individual HPA responsiveness to acute stress and its vasopressinergic regulation in old female rhesus monkeys that differ in their behavioral responses to stress. Animals with depression-like or anxiety-like behavior (DAB) responded with higher plasma levels of ACTH and AVP, lower levels of corticosteroids and higher cortisol/DHEAS molar ratios to restraint stress and to insulin-induced hypoglycemia compared with animals with healthy adaptive behavior. AVP and ACTH dynamics were closely correlated in most animals. AVP treatment produced differences in HPA responses similar to those produced by the stressors. The ACTH response to hypoglycemic stress in the DAB animal with highest HPA responsiveness was dramatically reduced by prior administration of a V1b receptor antagonist. These results suggest that the dysfunctions of HPA observed in old animals with DAB are caused by increased tone of the vasopressinergic system in regulation of HPA stress reactivity.
Highlights
Stress adaptation is fundamental for health, and the hypothalamic-pituitary-adrenal (HPA) axis is one of its main mechanisms
Our results illustrate that old female rhesus monkeys differ in their behavioral responses to stress and in HPA axis stress responsiveness
Animals with depression-like or anxiety-like behavior (DAB) responded with higher plasma levels of ACTH and arginine vasopressin (AVP), lower levels of corticosteroids and higher cortisol/dehydroepiandrosterone sulfate (DHEAS) molar ratios to restraint stress and to insulin-induced hypoglycemia compared with animals with SB
Summary
Stress adaptation is fundamental for health, and the hypothalamic-pituitary-adrenal (HPA) axis is one of its main mechanisms. Considerable data indicate that arginine vasopressin (AVP) related disturbances of stress adaptation can occur with aging [1]-[10]. Most studies of such kind have been performed on rodents, give contradictory results and fail to consider individual characteristics of the animals [1] [5]-[7]. There is evidence that links behavioral features of the individual with peculiarities in their HPA axis function [3] [4] [8] [11]-[14]. Hyperactivation of the HPA axis occurs in persons who exhibit increased anxiety, in those with some forms of depression [15]-[18] as well as in animals with depression-like behavior [11]-[19]. There are data showing a decline in dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S) secretion in depressed persons [20] [21]
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