Acute noise stress, ACTH administration, and blood pressure alteration.

Two groups of male Wistar rats were submitted to a single noise exposure (2640 Hz, 30 W, 102 dB, 15 min) (St group) or to a single dose of ACTH (1.5 IU/100 g b.wt.) (Ac group), respectively. A control group of nontreated rats (Co group) was used. Blood pressure (BP) was measured using an indirect tail cuff method and corticosterone (B) levels were measured by specific RIA. Haematocrit (Hc) and blood pH values were also evaluated. Acute treatments of both noise exposure and ACTH administration produced corticosterone hypersecretion and blood pressure elevation, with lower haematocrit and higher blood pH values than those found in the Co group. No differences were found between St and Ac treatments.