Control of physical exercise of rats in a swimming basin.

To study the mutual interaction between physical exercise and antioxidant systems in rats, we selected swimming as a model for exercise performance. Swimming belongs to the natural behavior of a rat, which under proper experimental conditions, primarily involves physical exercise with little emotional arousal. Therefore, we developed a swimming basin in which the intensity of exercise was manipulated by swimming speed and swimming duration. A laser beam interruption system enables recording of swimming patterns. For comparison we also used the basin to induce emotional arousal. Hereto the basin was transformed into a maze, in which unexpected blockade of a learned swimming route induced a panic-like emotional reaction. The antioxidant enzyme superoxide dismutase decreased in rat plasma after emotional arousal, not after physical exercise. Depletion of the antioxidant glutathione in the liver by diethyl maleate led to decrease of swimming performance. Noradrenaline but not adrenaline plasma levels increased in response to physical exercise. After emotional arousal the ratio noradrenaline/adrenaline did not change. In contrast, lactate only increased in response to emotional arousal. Plasma levels of glucose increased after both stress situations. Beta-adrenoceptor function, determined in the heart and in erythrocytes, only changed after physical exercise. The sensitivity to the beta-agonist (-)isoprenaline in the right atrium decreased and a downregulation of the beta-adrenoceptor density was observed in the erythrocyte.