In the present study, using quantitative receptor autoradiography and in situ hybridization histochemistry the effects of unilateral 6-hydroxydopamine lesions on the binding density levels of dopamine D1 and D2 receptors and the levels of mRNA encoding D1 and D2 receptors were investigated in the core and shell territories of the nucleus accumbens (Acb) and in the caudate-putamen (CP). The lesions induced contrasting effects on the D1 binding and D1 mRNA in the Acb and CP, i.e. an increase in binding and a decrease in the mRNA levels. For the D2 receptor an increase in both the binding density and mRNA levels was observed. The lesion-induced effects displayed regional differences. For D1 mRNA and D1 and D2 binding, the lesion effect was more pronounced in the core than in the shell of the Acb. For the D2 mRNA levels an increase was observed in the CP but not in the two territories of the Acb. Furthermore, the decrease in D1 mRNA was greater in the rostral than in the caudal parts of the core and shell of the Acb. These results indicate that the core and shell of the Acb and the CP respond differentially to dopamine depletion.