Persistent, specific and dose-dependent effects of toluene exposure on dopamine D2 2 agonist binding in the rat caudate-putamen

Abstract

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 IC 50 values (significant effects attained at 80 ppm), the K H, the K L, and the R H% 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 K D or the B max values of [ 3H]raclopride-binding in the caudate-putamen and the sub-cortical limbic area, or the IC 50 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 (≥ 80 ppm), but not xylene (80 ppm) or styr-ene (40 ppm), leads to persistent increases in the affinity of dopamine D2 2agonist binding in the rat caudate-putamen.