Effects of Ozone Exposure on the Circadian Variation in Wheel-running Activity in Rats
1985 Volume 20 Issue 4 Pages 301-307
Details
1985 Volume 20 Issue 4 Pages 301-307
The purpose of this study was to examine effects of ozone (O3), a main component of photochemical oxidants, on circadian variation in wheel-running activity in rats under 9: 15 hr light-dark situation (light period: 9-18 O'clock, dark period: 18-9 O'clock).
Male rats of the Wistar strain of 6-7, 11-12 and 22-24 weeks old were singly exposed to 0.25, 0.5 and 1.0ppm of O3 or repeatedly exposed to 0.25, 0.5 and 1.0 ppm of O3 on the days respectively 1, 2 and 3 for each 3 hr from 19 to 22 O'clock.
The results obtained were as follows:
1) The rats showed a circadian pattern of wheel-running activity with a higher and lower activities during dark and light period, respectively.
2) The rats of 6-7 and 11-12 weeks old showed significant decreases in the activity counts during the O3exposure. However, 22-24 weeks old rats did not show a marked change in the activity during O3 exposure, because the activity level of the rats was much lower than those of the 6-7 and 11-12 weeks old.
3) A significant increase in the activity was frequently observed after the termination of repeated O3 exposure.
Although the mechanisms of O3-induced changes in wheel-running activity in rats are not elucidated enough, the behavioral study is considered to be applicable for the evaluation of toxicity at low concentrations of O3.
