Nicotinic or ionotropic acetylcholine receptors (iAChRs) mediate excitatory signaling throughout the nervous system, and the heterogeneity of these receptors contributes to their multifaceted roles. Our recent work has characterized a single iAChR subunit, ACR-12, which contributes to two distinct iAChR subtypes within theC. elegansmotor circuit. These two receptor subtypes regulate the coordinated activity of excitatory (cholinergic) and inhibitory (GABAergic) motor neurons. We have shown that the iAChR subunit ACR-12 is differentially expressed in both cholinergic and GABAergic motor neurons within the motor circuit. In cholinergic motor neurons, ACR-12 is incorporated into the previously characterized ACR-2 heteromeric receptor, which shows non-synaptic localization patterns and plays a modulatory role in controlling circuit function.1In contrast, a second population of ACR-12-containing receptors in GABAergic motor neurons, ACR-12GABA, shows synaptic expression and regulates inhibitory signaling.2Here, we discuss the two ACR-12-containing receptor subtypes, their distinct expression patterns, and functional roles in theC. elegansmotor circuit. We anticipate our continuing studies of iAChRs in theC. elegansmotor circuit will lead to novel insights into iAChR function in the nervous system as well as mechanisms for their regulation.