Ozone-induced bradycardia and arrhythmia and their relation to sleep-wakefulness in rats.

Rats were chronically implanted with electrodes for EEG, EMG and ECG recordings and exposed to 0.1 ppm, 0.2 ppm ozone (O3) or clean air as control for 5 consecutive days. Amounts of wakefulness (W), slow-wave sleep (SWS) and paradoxical sleep (PS) of the O3-exposed rats were not statistically different from respective control values. Compared with control rats, heart rates of the O3-exposed rats decreased and the number of bradyarrhythmic episodes increased with an increase in O3 levels. The O3-induced bradyarrhythmias occurred more prevalently in the order of W, SWS and PS state. Parasympathetic mechanisms were suggested on those cardiac abnormalities.