Effects of toluene exposure on the spontaneous cortical activity in rats.

Effects of toluene on the electroencephalogram (EEG) and its power spectra were measured during a 2-hr exposure in a dynamic inhalational chamber in rats. Rats were exposed to one of six graded concentrations (110.6, 162.5, 432, 676, 1558, 2730 ppm) of toluene on different days. It was found that the duration of waking (W) was increased with a decrease in duration of rapid eye movement (REM) sleep even at 110.6 ppm. Duration of nonrapid eye movement (NREM) sleep was decreased with an increase of W and a decrease of REM sleep at 162.5 ppm. Dose-related effects were noted in higher concentrations. The power of delta frequency band was increased with a decrease of theta frequency band power at hr 1 of exposure to 676 ppm during REM sleep recorded from the visual cortex. The power of theta frequency band was also decreased at hr 2 of exposure at 432 ppm. During W and NREM sleep power spectra were not changed significantly. Results indicate that the changes of EEG are a sensitive measure of the effects of toluene on the central nervous system (CNS).