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Behavioral Effects of Sub-Acute Inhalation of Toluene in Adult Rats
Citation:
BEASLEY, T. E., P. A. EVANSKY, AND P. J. BUSHNELL. Behavioral Effects of Sub-Acute Inhalation of Toluene in Adult Rats. NEUROTOXICOLOGY AND TERATOLOGY. Elsevier Science Ltd, New York, NY, 34(1):83-89, (2011).
Impact/Purpose:
Toluene is the most commonly emitted hazardous air pollutant making it a major public health concern. Effects of acute exposure to toluene are well characterized whereas the evidence for persistent effects of repeated toluene exposure is mixed and therefore inconclusive. The research reported in this paper sought to determine whether 4 weeks of repeated, 6-hour daily exposures to toluene vapor altered acquisition of an autoshaped lever press response that was observed in a previous 13 week toluene exposure (Beasley et al., 2010), and to determine whether this sub-acute exposure affected sustained attention as assessed by a signal detection method. Motor activity and anxiety-related behavior were unaffected by toluene. Sub-acute toluene also did not affect the acquisition of the lever press response or the visual discrimination task. However,it did reduce the accuracy of signal detection at the end of training.Analysis of the accuracy deficit in the 1000 ppm group by parametric manipulations suggested a greater influence of attentional impairment than visual or motor dysfunction. Therefore, these studies provide little evidence for persistent effects of inhaled toluene on cognitive function in rats. This information will be useful for periodic evaluations of the reference concentration for toluene in the IRIS database.
Description:
Reports of behavioral effects of repeated inhalation of toluene in rats have Yielded inconsistent fmdings. A recent study from this laboratory (Beasley et al., 2010) observed that after 13 weeks of inhaled toluene ("sub-chronic" 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 (O, 10, 100, or 1000 ppm) for 6 hr/day, 5 days/week for 4 weeks. As in the sub-chronic 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. Analysisof the deficit in accuracy in the 1000 ppm group by means of manipulations of different task parameters suggested a greater influence 0f 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 toluene vapor, in contrast to robust and reliable effects of acute inhalation of the solvent.
