Cholinergic signaling plays a crucial role in the function of the vestibular and auditory systems. Acetylcholine (ACh) is the primary neurotransmitter in cholinergic signaling. ACh is released by auditory and vestibular efferent neurons and acts on both muscarinic and nicotinic acetylcholine receptors. Cholinergic signaling can enhance or inhibit the sensitivity of hair cells, and therefore modulate their responses to mechanical stimuli. Imbalances in the production, release, or breakdown of ACh can disrupt normal vestibular signaling. We are examining the role supporting cells (SCs) play in cholinergic signaling in these systems and how that regulates physiological function.