Expression pattern of JunD after acute or chronic l-DOPA treatment: Comparison with ΔFosB

In this study, we have used 6-hydroxydopamine-lesioned rats to examine changes in striatal junD and fosB/ΔfosB expression induced by acute and chronic treatment with l-DOPA (5 and 15 days). Changes at the protein levels were studied using Western immunoblotting while mRNA changes were compared using in situ hybridization histochemistry. We observed a significant increase in the level of ΔFosB proteins after chronic treatment with l-DOPA, an effect that was not observed for JunD proteins. In addition, the upregulation of ΔFosB was already present after an acute treatment but increased upon chronic treatment. By contrast, junD and ΔfosB mRNA were both upregulated significantly above control levels after an acute injection of l-DOPA. In conclusion, this study suggests a differential expression pattern of junD and ΔfosB in a rat model of l-DOPA-induced dyskinesia. The upregulation of ΔFosB protein, but not JunD, is likely to reflect an increased stability of the ΔFosB proteins without ongoing enhanced transcription of the encoding genes.