Uribe-Cano, S.; Kottmann, A. H.

The striatum is a hub for associative learning where fluctuations in dopamine (DA) and acetylcholine (ACh) dynamically regulate behavior. ACh is released by cholinergic interneurons (CIN), which integrate diverse inputs to contextualize DA signals and shape adaptive responses. Among these inputs, we previously observed that the GPCR Smoothened (Smo) on CIN suppresses L-DOPA-induced dyskinesias, a motor side-effect resulting from artificially elevated DA levels in the Parkinsonian brain. Here, we examine whether Smo signaling modulates ACh dynamics, its coordination with DA, and motor learning in the healthy brain. We find that CIN-specific Smo activity bidirectionally modulates ACh inhibition in response to both optogenetically evoked and endogenous DA. Smo relieves DA-associated ACh inhibition and permits its progressive modification with repeated DA release. These effects alter the temporal organization of ACh in the dorsolateral striatum and its coupling to DA, without affecting DA release itself. Behaviorally, Smo ablation from cholinergic neurons promotes initial motor learning at the expense of future behavioral flexibility. Together, these findings identify Smo as a bidirectional modulator of striatal DA-ACh coordination and striatal learning.