Toluene Inhalation Increases Extracellular Noradrenaline and Dopamine in the Medial Prefrontal Cortex and Nucleus Accumbens in Freely-Moving Rats

Toluene is a major component of thinner, which can cause intoxication with inhalation. Until recently, there were little experimental data focusing on the neuropharmacological effects of toluene. In this study, central effects caused by toluene were examined. Noradrenaline and dopamine levels in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAcc) were studied in freely-moving rats during exposure to inhaled toluene, using in vivo microdialysis. Toluene inhalation at 7,000 ppm increased extracellular noradrenaline and dopamine levels in both the mPFC and the NAcc. In the NAcc, noradrenaline and dopamine increased to 210% and 178% of their respective baseline values. In the mPFC, noradrenaline and dopamine increased to 306% and 183%, respectively. At both sites, the increase of noradrenaline was greater than that of dopamine. Toluene inhalation at 1,000 ppm and 3,000 ppm did not significantly affect extracellular noradrenaline and dopamine levels. It became clear that toluene inhalation was involved in the mesolimbic dopamine system which plays an especially important part in the drug dependence. These results also suggest that exposure to toluene by inhalation enhances excitability of noradrenergic neurons.