Chronic noise stress and dexamethasone administration on blood pressure elevation in the rat

In order to evaluate the role of ACTH and corticosterone in the elevated blood pressure produced by chronic noise, we have studied the effect of dexamethasone administration on blood pressure. Adrenal response was measured by alterations in plasma corticosterone levels in two experimental groups (Dexamethasone treated rats, Dexamethasone-noise stressed rats) and compared with a Control and a Noise-stressed group. Chronic noise stress with a frequency of 2640 Hz, power of 30 w and duration of 15 min daily was used for 30 consecutive days. Dexamethasone was administered by subcutaneous injection of 100 micrograms/100 g b.wt daily. Blood pressure was measured by an indirect tail cuff method and corticosterone levels by specific RIA. Dexamethasone administration decreases corticosterone levels but increases blood pressure. Dexamethasone-treated noise stressed rats show higher residual corticosterone levels and a more marked increase on blood pressure than rats treated with dexamethasone alone. Thus noise-stress and dexamethasone administration have opposing effects on corticosterone release and a synergistic effect on blood pressure elevation.