RUNNING TRAINING ATTENUATES THE ACTH RESPONSES IN RATS TO SWIMMING AND CAGE-SWITCH STRESS

The present study was carried out to investigate the effect of running training on adrenocorticotrophic hormone (ACTH) response in rats to swimming or cage-switch stress to determine whether, after physical training, a cross-adaptation develops in the ACTH responses induced by different types of stresses. Rats were trained by two different kinds of exercises and for two different periods of training: 1) swimming for 4 wk (4W-swimming), 2) running for 4 wk (4W-running), and 3) running for 10 wk (10W-running). Remaining rats were used for control for 4 wk (4W-control) and 10 wk (10W-control). The ACTH response induced by swimming stress was reduced after training by swimming (62.4%) or by running (13.8-16.4%). These training periods also attenuated the ACTH response induced by cage-switch stress (62.4% in the swimming group, 23.8-34.6% in the running groups). After swimming stress, the 4W-swimming and 10W-running groups showed smaller increases in blood glucose than the control groups. In addition, the increased levels of blood lactate in all the trained rats were significantly smaller than those in the control groups, suggesting that an adaptation was achieved after physical training. These results suggest that after running training, cross-adaptation is developed in the ACTH response induced by different types of physical (swimming) or psychological (cage-switch) stresses.