Behavioral effects of sub-acute inhalation of toluene in adult rats

Reports of behavioral effects of repeated inhalation of toluene in rats have yielded inconsistent findings. A recent study from this laboratory (Beasley et al., 2010) observed that after 13 weeks of inhaled toluene (“subchronic” exposure scenario), rats showed mild but persistent changes in behavior, primarily involving acquisition of an autoshaped lever-press response. The present experiment sought to systematically replicate these findings, using a 4-week “sub-acute” exposure scenario. Adult male Long–Evans rats inhaled toluene vapor (0, 10, 100, or 1000 ppm) for 6 h/day, 5 days/week for 4 weeks. As in the subchronic study, toluene had no effect on motor activity, anxiety-related behavior in the elevated plus-maze, or acquisition of the visual discrimination. However, sub-acute toluene did not affect appetitively-motivated acquisition of the lever-press response, but did reduce accuracy of signal detection at the end of training. Analysis of the deficit in accuracy in the 1000 ppm group by means of manipulations of different task parameters suggested a greater influence of attentional impairment than visual or motor dysfunction as a source for the deficit. These results confirm a pattern of subtle and inconsistent long-term effects of repeated daily exposure to concentrations of toluene vapor of 1000 ppm and below, in contrast to robust and reliable effects of acute inhalation of the solvent at concentrations above 1000 ppm.

► Adult rats inhaled toluene (≤ 1000 ppm) daily (6 h/day) for 4 weeks.
► Post-exposure tests included activity, anxiety, learning and visual signal detection.
► 1000 ppm toluene altered signal detection, suggesting attention deficits.
► Repeated toluene did not impair behavior as previously reported by others.