DIFFERENTIAL-EFFECTS OF DOPAMINE DEPLETION ON THE BINDING AND MESSENGER-RNA LEVELS OF DOPAMINE-RECEPTORS IN THE SHELL AND CORE OF THE RAT NUCLEUS-ACCUMBENS

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 D-1 and D-2 receptors and the levels of mRNA encoding D-1 and D-2 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 D-1 binding and D-1 mRNA in the Acb and CP, i.e. an increase in binding and a decrease in the mRNA levels. For the D-2 receptor an increase in both the binding density and mRNA levels was observed. The lesion-induced effects displayed regional differences. For D-1 mRNA and D-1 and D-2 binding, the lesion effect was more pronounced in the core than in the shell of the Acb. For the D-2 mRNA levels an increase was observed in the CP but not in the two territories of the Acb. Furthermore, the decrease in D-1 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 CP respond differentially to dopamine depletion.