Changes in electrocortical arousal following acute trimethylbenzene administration in rats

The purpose of this investigation was to compare the neurotoxic potential of trimethylbenzene (TMB) isomers (the solvents) with that of benzene derivatives with a smaller number of methyl groups (toluene). The experiments were performed on WAG/Rij rats with EEG recording electrodes implanted in the fronto-parietal cortex. The solvents, toluene or TMB isomers: 1,3,5-TMB (mesitylene), 1,2,3-TMB (hemimellitene) or 1,2,4-TMB (pseudocumene), were diluted with olive oil and administered intragastrically via gavage at an acute dose of 0.002, 0.008, or 0.032 mol/kg. The electrocortical activity was recorded for 20 min before, and for 60 min after the solvent administration. The electrocorticograms were analysed with respect to the number and duration of the high-voltage spindles (HVS), a form of activity sensitive to the arousal level. In case of each solvent the observed effect--inhibition of the HVS activity--was dose-related. However, the effect produced by TMB isomers was in each case less pronounced than that of toluene. Among TMBs, pseudocumene displayed the least significant effect, and the efficacy of two other TMB isomers was similar.