Morphological dendritic spine changes of medium spiny neurons in the nucleus accumbens in 6-hydroxydopamine-lesioned rats treated with levodopa.

The mechanisms of dopamine dysregulation syndrome (DDS) in Parkinson's disease (PD) remain unclear, although it is known that the nucleus accumbens (NAc) plays a role in its development. Based on the hypothesis that DDS and levodopa-induced dyskinesia (LID) share a pathophysiological basis, we investigated dendritic spine morphology of medium spiny neurons (MSNs) in the NAc of a rat model of LID, because spine enlargement in MSNs of the caudate/putamen has been proposed to be a morphological hallmark of LID. Spines of NAc MSNs also became enlarged in the LID model. This result suggests that excitatory supersensitivity of MSNs in the NAc is involved in the development of DDS, similar to what occurs in the caudate/putamen in LID.