The effects of acute and repeated toluene exposure on operant behavior in mice

Adult male CD-1 mice were trained on a differential reinforcement of low rate (DRL) 10-sec schedule for milk presentation during 15-min sessions. After training, an initial concentration-effect curve was determined for acute exposure to toluene (200-6400 ppm). Exposures were carried out in a static exposure chamber for 30 min; operant sessions began immediately after removal from the chamber. Mice were exposed to air under the same conditions on days they were not exposed to toluene. Response rate increases were seen at low concentrations and decreases at higher concentrations (greater than 3200 ppm). The rate of reinforcement decreased in a concentration-dependent manner. Mice were then exposed to 6000 ppm toluene for 30 min daily, 7 days a week for 7 weeks, immediately before each session. During this time the response rate was variable, but reinforcement rate remained consistently low. Following the termination of chronic toluene exposure, a second concentration-effect curve was determined which was not significantly different from the initial curve. There was, however, a nonsignificant tendency towards higher response rates at the rate-increasing concentrations. Thus after repeated exposures no tolerance to toluene was seen under these test conditions.