Assous, M.; Kocaturk, S.; Guven, E. B.; Tepper, J. M.

Striatal cholinergic interneurons (CINs) exhibit a transient pause in tonic firing in response to salient stimuli, a hallmark of reinforcement learning that becomes synchronized with learning. Although thalamostriatal and dopaminergic inputs have been implicated in this pause, the underlying circuit mechanisms remain unclear. Here, we combine optogenetics, electrophysiology, and genetic approaches to examine inhibitory interactions within the CIN network. Synchronized activation of CINs in striatal slices elicited robust feedback inhibition in CINs, suppressing firing and generating pause-like responses. This inhibition was mediated by GABAA receptors and required beta2-containing nicotinic acetylcholine receptors (beta2-nAChR), and could be recruited by thalamostriatal activation. Dopamine is not required for this circuit but modulates it via D2 receptors. Surprisingly, cell-type-specific silencing and striatal beta2-nAChR deletion excluded local GABAergic sources, whereas retrograde beta2-nAChR deletion abolished inhibition, revealing an extrastriatal pathway. These findings identify a long-range inhibitory mechanism linking synchronized cholinergic activity to pause generation in striatal circuits.