Neuroleptics differentially modulate central dopamine D1-receptor binding.

The effect of the classical neuroleptic, fluphenazine, on dopamine D1-receptor binding was examined in different regions of the basal ganglia. Whereas exposure to fluphenazine for 18 months reduced [125I]SCH-23982 binding to D1-receptors in the caudate putamen, nucleus accumbens and olfactory tubercle, binding in the entopeduncular nucleus was enhanced after fluphenazine treatment. Competition studies indicated that the region-dependent changes in [125I]SCH-23982 binding after fluphenazine exposure were not due to differences in the affinity of fluphenazine or other dopamine ligands for D1-binding sites. These data suggest that in addition to modulating striatal function, classical neuroleptics may also alter neurotransmission in the basal ganglia by enhancing dopamine receptor binding in the entopeduncular nucleus.