[A chronobiological study on toluene anesthesia in mice].

An experimental study of toluene exposure was performed on mice at various times of the day using the righting reflex and blood concentration as indicators. One hundred and sixty ICR mice were housed 8 mice per cage for 3 weeks with free access to food and water under a dark-light cycle consisting of alternate 12 hr periods of darkness and light: the dark period beginning at 7:00. The exposure was begun when the mice were 8 weeks old. They were exposed to 10,000 ppm of toluene for 40 min at 4:00, 10:00, 16:00 and 22:00, and they were sacrificed at the end of the exposure, after 3 min or after 30 min. The duration of anesthesia was 200.2 +/- 15.4 (sec) at 4:00, 361.1 +/- 21.5 (sec) at 10:00, 335.1 +/- 18.5 (sec) at 16:00 and 309.2 +/- 19.8 (sec) at 22:00. The duration of anesthesia at 4:00 was shorter than that of the other times of the day statistically (p less than 0.01). With regard to the toluene concentration in blood, there was no significant difference between those mice sacrificed at the end of exposure and those sacrificed after 3 min.