Modification of rat operant behavior by ozone exposure

Ozone exposure may induce extrapulmonary consequences, such as reductions in the spontaneous activity of rodents, or complaints in humans of lethargy, headache, chest discomfort, and other subjective symptoms. Further evidence of behavioral disruption was provided by this experiment. Twelve rats were trained to perform a bar-pressing response maintained by food reward. Food pellets were delivered according to a fixed interval 5-min reinforcement schedule. Exposures encompassed a range of concentrations from 0.1 to 2.0 ppm. A single exposure lasted 6 hr, and successive exposures were separated by at least 6 days. Compared to performance under control conditions (ambient air), response rates fell linearly from 0.1 to 1.4 ppm. During individual 6-hr exposures, the rates declined from the beginning to the end of the session. These results, given the sedentary nature of the task, reflect reduced inclination rather than impaired physiological capacity to respond.