Effects of acute exposure to aromatic hydrocarbons C 9 on locomotor activity in rats. Trimethylbenzene isomers.

This study was performed to find out whether in acute exposure to trimethylbenzene (TMB) isomers the dose effect relationship is linear or biphasic. In experiments performed on rats, the effect of four solvents was studied: three TMB isomers: 1,3,5-TMB (mesitylene), 1,2,3-TMB (hemimellitene), and 1,2,4-TMB (pseudocumene), and toluene, known for its biphasic activity, was used as a reference compound. The solvents were dissolved in olive oil and administered to rats orally at the doses of 0.008, 0.016, and 0.032 mol/kg. Spontaneous locomotor activity was assessed with the open-field test. Solvent concentrations in peripheral blood were determined parallelly by gas chromatography on separate groups of animals. Statistics employed a two-way analysis of variance (ANOVA) and Tukey's test. The results showed that oral administration of toluene at a dose of 0.008 mol/kg induced biphasic changes in the animal locomotor activity. It was found that TMB at applied doses increased slightly the animal locomotor activity, but the magnitude of changes did not indicate their stimulating effect. Contrary to toluene, no time-effect relationship was observed after administration of trimethylbenzene isomers. The mean blood concentrations of solvents were dose-related. The highest concentrations were observed after toluene administration.