Persistent, specific and dose-dependent effects of toluene exposure on dopamine D2 agonist binding in the rat caudate-putamen.

Exposure to toluene (40-320 ppm; 4 weeks, 6 h/day, 5 days/week), followed by a postexposure period of 29-40 days, decreased the wet weight of the caudate-putamen and of the subcortical limbic area (maximal effect of 10% attained at 80 ppm toluene) of the male rat. Furthermore, toluene exposure decreased the IC50 values (significant effects attained at 80 ppm), the KH, the KL, and the RH% values of dopamine on [3H]raclopride-binding in the caudate-putamen. Toluene exposure did not significantly affect either the body weights, the wet weights of the whole brain, the serum prolactin levels, the KD or the Bmax values of [3H]raclopride-binding in the caudate-putamen and the subcortical limbic area, or the IC50 values of dopamine at [3H]raclopride-binding sites in the subcortical limbic area. Exposure to xylene or styrene (80 and 40 ppm, respectively; 4 weeks, 6 h/day, 5 days/week), followed by a postexposure period of 26-32 days, had no effect on the parameters described above (prolactin levels were not analyzed). The present study indicates that long-term exposure to low concentrations of toluene (> or = 80 ppm), but not xylene (80 ppm) or styrene (40 ppm), leads to persistent increases in the affinity of dopamine D2 agonist binding in the rat caudate-putamen.