Neurotoxic effects of acute and subchronic inhalation exposure to trimethylbenzene isomers (pseudocumene, mesitylene, hemimellitene) in rats.

Neurotoxic effects of trimethylbenzene isomers (pseudocumene, mesitylene and hemimellitene) in male rats were investigated in conditions of acute and subchronic inhalation exposure. Rotarod performance and pain sensitivity behaviour were tested in rats exposed to trimethylbenzenes at concentrations of 250-2,000 ppm immediately after termination of a 4-hour exposure. Exposure to each of trimethylbenzene isomers resulted in concentration-dependent disturbances in rotarod performance, and decrease in pain sensitivity in rats. Pseudocumene, mesitylene and hemimellitene EC50 values for rotarod performance behaviour disturbances were 954, 963, 768 ppm and for decreases in pain sensitivity EC50 were 1,115, 1,212, 848, ppm, respectively. In conditions of subchronic inhalation exposure, pseudocumene and hemimellitene at concentrations of 25, 100 and 250 ppm caused concentration-dependent disturbances in rotarod performance behaviour and decrease in pain sensitivity. Neurotoxic effect of hemimellitene was more pronounced than that of pseudocumene and mesitylene. Two weeks after cessation of inhalation exposure to pseudocumene or hemimellitene no recovery in rotarod performance behaviour was observed.