PERSISTENT, SPECIFIC AND DOSE-DEPENDENT EFFECTS OF TOLUENE EXPOSURE ON DOPAMINE D-2 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 K-H, the K-L, and the R(H)% values of dopamine on [H-3]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 K-D or the B-max values of [H-3]raclopride-binding in the caudate-putamen and the subcortical limbic area, or the IC50 values of dopamine at [H-3]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 (greater than or equal to 80 ppm), but not xylene (80 ppm) or styrene (40 ppm), leads to persistent increases in the affinity of dopamine D-2 agonist binding in the rat caudate-putamen.