Dopamine 2 receptor ablation from cholinergic neurons attenuates L-DOPA induced dyskinesias

L-DOPA-induced dyskinesia (LID) formation requires prominent dopamine oscillations over hours, across years of treatment. Striatal cholinergic interneurons (CIN) have been implicated in both the facilitation and attenuation of LID, but how CIN sense and respond to striatal dopamine levels in this context remains incompletely understood. CIN express both the inhibitory, Gα_i-coupled dopamine D2 receptor and the facilitatory, Gα_s-coupled dopamine D5 receptor. Although systemic ablation of D5 exacerbates LID, the contribution of CIN-specific D2 expression to LID has not been studied.

We generated mice with conditional ablation of D2 from choline acetyltransferase-expressing cells (D2_ChATKO) and subjected them to unilateral 6-hydroxydopamine lesions followed by chronic L-DOPA dosing. We assessed dyskinetic behaviors across escalating L-DOPA doses and performed postmortem analyses of LID-associated signaling markers in dorsal striatal CIN. Specifically, we quantified p-ERK expression and phosphorylated rpS6^240/244, a marker of translational activity, in CIN from mice examined in the L-DOPA ON and OFF states.

D2_ChATKO mice exhibited attenuated LID across escalating L-DOPA doses. Postmortem analyses suggested reduced expression of the LID-associated marker p-ERK among CIN of the dorsal striatum. In control mice, L-DOPA increased phosphorylated rpS6^240/244 in a subset of CIN located in the dorsolateral striatum, indicating increased translational activity during the L-DOPA ON state. Ablation of D2 from CIN prevented this L-DOPA-associated increase in CIN phosphorylated rpS6^240/244.

Together, these findings indicate that D2 signaling in CIN promotes LID formation and suggest that CIN D2 is a potential molecular target for mitigating dyskinesias while preserving the therapeutic efficacy of L-DOPA. These results are discussed in the context of recently refined models of how CIN may contribute to aberrant plasticity in the basal ganglia of the Parkinsonian mouse brain.