Vasopressin and urine flow rate responses to stress in conscious dogs

Abstract

Behavioral stress increases arterial pressure while decreasing urine flow rate; the urine flow rate response can be abolished by surgical renal denervation. In this study, the effects of infusion of alpha-adrenoceptor antagonists (intravenous phenoxybenzamine or prazosin) on the antidiuretic and plasma vasopressin responses to stress were examined. Without alpha-adrenoceptor blockade, 20 min of stress increased arterial pressure and decreased urine flow rate, but no change in urine osmolality or plasma vasopressin concentration occurred. Arterial pressure and urine flow rate returned to base-line level during a 20-min recovery period. With alpha-adrenoceptor blockade, which prevented the arterial pressure response to stress, urine flow rate still decreased during stress, but urine osmolality and plasma vasopressin concentration increased. The decrease in urine flow rate and increase in urine osmolality and plasma vasopressin concentration persisted into the first 20-min recovery period but returned to base-line level during a second 20-min recovery period. We conclude that the antidiuretic response to behavioral stress in conscious dogs with saline infusion alone is not mediated via a change in vasopressin release. In contrast, the antidiuretic response to behavioral stress with alpha-adrenoceptor antagonist infusion may be mediated via an increased release of vasopressin.

Sinoaortic Denervation Does Not Increase Cardiovascular/ Endocrine Responses to Stress

“…Stressful stimuli are known to activate the anterior pi tuitary ACTH, prolactin, adrenal corticosteroids, cate cholamines and posterior pituitary OT[l 1,13,14,21,29,30]. There is conflicting evidence concerning the effect of SAD on stress-induced endocrine responses.…”

“…In con trast, Alexander and colleagues [3] found that restraint stress caused similar increases in arterial pressure, cate cholamines and dopamine-[3-hydroxylase levels in SAD and control animals. VP has been shown to be unrespon sive to numerous types of stress [10][11][12][13][14]30]. However, Koepke et al [14] reported that plasma VP was elevated by air stress in dogs which were pretreated with an a-adrenergic receptor antagonist [14], They suggested that the removal of a negative feedback of arterial pressure follow ing stress could unmask an endogenous VP response.…”

“…There is almost universal agreement that OT is a stress-responsive hormone [10,11]. In contrast, the evidence suggests that VP is relatively insensitive to a vari ety of stressors, including mild restraint, cold and exercise [10][11][12][13][14]. In a previous report, Koepke et at.…”

“…In a previous report, Koepke et at. [14] showed that a stress-induced VP response could be elicited only after the induction of a-adrenergic receptor blockade. The authors speculated that an increase in arterial pres sure caused a neurally mediated inhibition of VP secre tion and that removal of the pressor response unmasked the hormonal response.…”

Role of anteroventral third ventricle and vasopressin in renal response to stress in borderline hypertensive rats.

“…Koepke et al 33 reported antidiuresis and increased plasma vasopressin concentration with avoidance training in dogs. Likewise, Onaka et al 34 observed an increase in plasma vasopressin concentration to foot shock.…”