Acute Effects of Ozone on Heart Rate and Body Temperature in the Unanesthetized,Unrestrained Rat Maintained at Different Ambient Temperatures

摘要

The present studies were conducted to investigate the concentration-responsecharacteristics of acute ozone (O3) exposure on the cardiovascular and thermoregulatory function of the unanesthetized, unrestrained rat, and to examine the modulating effects produced by changes in ambient temperature (T(sub a)) on the induced toxic response. For all studies, groups of male Fischer 344 rats (n=4-6/group) were implanted with radiotelemetry transmitters and allowed to recover overnight. The transmitters permitted continuous monitoring of electrocardiogram (ECG) and body core temperature (T(sub co)); heart rate (HR) was derived from the ECG signal. Frequency of breathing (f) was obtained in selected experiments by means of a Fenn box. All animals were monitored according to the following protocol: control (filtered air; 0.25 h); exposure (O3; 2 h); recovery (filtered air; 3-18 h). For the concentration-response experiments, O3 concentration was varied from 0.25-1.0 ppm and all exposures were conducted at an T(sub a) of 18-20 C. Significant decreases in HR and T(sub co) were demonstrated at O3 concentrations as low as 0.37 ppm.