Subchronic Inhalation Exposure to Acetone Vapor and Scheduled Controlled Operant Performance in Male Rats

Groups of adult male rats (10/group) were used to assess whether subchronic inhalation exposure to 0, 1000, 2000, or 4000 ppm of acetone vapor altered schedule-controlled operant performance. Rats were exposed to acetone vapor for 6 h/day, 5 days/wk, for a 13-wk period. Extensive training prior to the exposure series established a stable baseline of lever-pressing on a multiple fixed-ratio-fixed-interval (FR 20-FI 120 s) schedule of food presentation. Operant sessions occurred prior to each daily exposure to avoid confounding the detection of enduring behavioral effects with transient acute effects. FI response rate, FI index of curvature, and FR running rate of response were not affected during or after the 13-wk exposure series. FR post-reinforcement pause duration for the control group increased during the course of the study more than that of the 2000 ppm and 4000 ppm groups, which changed only slightly relative to pretreatment baseline. Based on the performance of historical controls that had FR pause durations similar to those of acetone-treated groups, the differences in FR pause duration were probably due to drift of the concurrent control group and were not related to acetone treatment. Prolonged exposure to up to 4000 ppm acetone vapor does not appear to have enduring effects on nervous system functions that mediate the performance of a complex, learned task.