Uribe-Cano, S. | bioRxiv Science

bioRxiv2025

The GPCR Smoothened on Cholinergic Interneurons Modulates Dopamine-associated Acetylcholine Dynamics

The striatum is a hub for associative learning where fluctuations in dopamine and acetylcholine dynamically regulate behavior. Acetylcholine is released by cholinergic interneurons, which integrate diverse inputs to contextualize dopamine signals and shape behavior. We previously observed that the GPCR Smoothened on cholinergic interneurons suppresses L-DOPA-induced dyskinesias, a motor side-effect resulting from medication elevated dopamine in the Parkinsonian brain. Here, we examine whether Smoothened signaling modulates acetylcholine dynamics, its coordination with dopamine, and motor learning in the healthy brain. We find that cholinergic neuron-specific Smoothened activity bidirectionally modulates acetylcholine inhibition following dopaminergic or cholinergic neuron activity. These effects alter the temporal organization of acetylcholine in the dorsolateral striatum and its coupling to dopamine. Behaviorally, Smoothened ablation from cholinergic neurons promotes motor learning and altered adjustment to changes in the effort or time to obtain reward. These findings identify Smoothened as a bidirectional modulator of striatal dopamine-acetylcholine coordination and striatal learning. HighlightsSonic Hedgehog-Smoothened signaling in striatal cholinergic interneurons bidirectionally regulates dopamine-associated cholinergic pauses without altering dopamine release. Cholinergic Smoothened shapes the timing, duration, and coordination of endogenous dopamine-acetylcholine dynamics in the dorsolateral striatum. Cholinergic Smoothened modulates striatal learning by accelerating motor learning while constraining effort management in an instrumental task. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/662982v2_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@12531d7org.highwire.dtl.DTLVardef@eb2620org.highwire.dtl.DTLVardef@140479org.highwire.dtl.DTLVardef@31cf0e_HPS_FORMAT_FIGEXP M_FIG C_FIG

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bioRxiv2024

L-Dopa induced dyskinesias require Cholinergic Interneuron expression of Dopamine 2 receptor.

Striatal cholinergic interneurons (CIN) have been implicated in both, the facilitation as well as the attenuation of L-DOPA-induced dyskinesias (LID). These findings indicate that CIN impinge on formation and expression of LID in a dopamine state dependent manner since LID formation requires prominent oscillations of dopamine at timescales of hours over several years. However, how CIN sense and interpret striatal dopamine levels is not completely understood. CIN express both inhibitory, high affinity, Gi coupled D2 (D2R)- and facilitatory, medium affinity, Gs coupled D5 (D5R)-dopamine receptors. While the systemic ablation of D5R exacerbates LID, the contribution of D2R expression in CIN to LID has not been studied. Here, we produced mice with conditional ablation of D2R from choline acetyltransferase-expressing cells (D2ChATKO) subjected to unilateral 6-hydroxydopamine lesions and chronic L-DOPA dosing. Behavioral assessments revealed that D2ChATKO mice exhibited attenuated LID across escalating L-DOPA doses. Postmortem analyses showed reduced expression of the LID-associated marker p-ERK in CIN in the dorsolateral striatum. Further, quantification of the CIN activity marker p-rpS6240/244 of mice in the L-DOPA ON and OFF state revealed that L-DOPA resulted in an increase of cholinergic activity driven by a subset of mainly dorso-laterally located CIN. D2R ablation from CIN prevented the L-DOPA associated increase in cholinergic activity. Together, these findings indicate that D2R signaling in CIN promotes LID formation, and they highlight CIN D2R as a potential molecular target for mitigating dyskinesias while preserving the therapeutic efficacy of L-DOPA. We discuss our results in the context of recently refined models how CIN contribute to aberrant plasticity in the basal ganglia of mouse models of Parkinsons Disease.

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