Activity-dependent and use-dependent regulation of dopamine-receptor clustering

In this study, fluorescence-conjugated ligands were employed to label dopaminergic D1-like and D2-like receptors, respectively, in neurons derived from the frontal cortex of embryonic rats. The receptor binding sites were visualized and analyzed using confocal microscopy. Our results showed that fluorescently labeled receptors tended to form clusters with a diameter of about one micrometer and were distributed on both somata and dendrites. Chronic treatment with tetrodotoxin reduced the number of fluorescent clusters of both D1-like and D2-like receptors, while chronic treatment with a high concentration of potassium increased the number of fluorescent clusters of both D1-like and D2-like receptors. Further, chronic treatment with SCH23390 up-regulated the number of D1-like receptor clusters, whereas chronic treatment with bromocriptine down-regulated the number of D2-like receptor clusters. In addition, chronic treatment with spiperone down-regulated the number of D1-like receptor clusters. These results suggest that both neuronal activity and dopaminergic receptor occupancy are important factors that determine dopaminergic receptor clustering which is an essential step toward synaptogenesis during neuronal maturation process.