title: Etiology of distinct membrane excitability in pre- and posthearing auditory neurons relies on activity of Cl- channel TMEM16A.
abstract: The developmental rehearsal for the debut of hearing is marked by massive changes in the membrane properties of hair cells (HCs) and spiral ganglion neurons (SGNs). Whereas the underlying mechanisms for the developing HC transition to mature stage are understood in detail, the maturation of SGNs from hyperexcitable prehearing to quiescent posthearing neurons with broad dynamic range is unknown. Here, we demonstrated using pharmacological approaches, caged-Ca(2+) photolysis, and gramicidin patch recordings that the prehearing SGN uses Ca(2+)-activated Cl(-) conductance to depolarize the resting membrane potential and to prime the neurons in a hyperexcitable state. Immunostaining of the cochlea preparation revealed the identity and expression of the Ca(2+)-activated Cl(-) channel transmembrane member 16A (TMEM16A) in SGNs. Moreover, null deletion of TMEM16A reduced the Ca(2+)-activated Cl(-) currents and action potential firing in SGNs. To determine whether Cl(-) ions and TMEM16A are involved in the transition between pre- and posthearing features of SGNs we measured the intracellular Cl(-) concentration [Cl(-)]i in SGNs. Surprisingly, [Cl(-)]i in SGNs from prehearing mice was ∼90 mM, which was significantly higher than posthearing neurons, ∼20 mM, demonstrating discernible altered roles of Cl(-) channels in the developing neuron. The switch in [Cl(-)]i stems from delayed expression of the development of intracellular Cl(-) regulating mechanisms. Because the Cl(-) channel is the only active ion-selective conductance with a reversal potential that lies within the dynamic range of SGN action potentials, developmental alteration of [Cl(-)]i, and hence the equilibrium potential for Cl(-) (ECl), transforms pre- to posthearing phenotype.
authors: Department of Internal Medicine, Division of Cardiovascular Medicine, School of Medicine, University of California, Davis, CA 95616;
authors: Xiao-Dong
authors: XD
authors: Zhang
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557;
authors: Jeong-Han
authors: JH
authors: Lee
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557; Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China;
authors: Ping
authors: P
authors: Lv
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557;
authors: Wei Chun
authors: WC
authors: Chen
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557;
authors: Hyo Jeong
authors: HJ
authors: Kim
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557;
authors: Dongguang
authors: D
authors: Wei
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557;
authors: Wenying
authors: W
authors: Wang
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557;
authors: Choong-Ryoul
authors: CR
authors: Sihn
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557;
authors: Karen Jo
authors: KJ
authors: Doyle
authors: Department of Anatomy, School of Medicine, University of California, San Francisco, CA 94143; and.
authors: Jason R
authors: JR
authors: Rock
authors: Department of Internal Medicine, Division of Cardiovascular Medicine, School of Medicine, University of California, Davis, CA 95616; Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655.
authors: Nipavan
authors: N
authors: Chiamvimonvat
authors: Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557; enyamoah@gmail.com.
authors: Ebenezer N
authors: EN
authors: Yamoah
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000075369:Anoctamin-1; D000075368:Anoctamins; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism; D005260:Female; D006309:Hearing / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010641:Phenotype; D064506:Solute Carrier Family 12, Member 2 / Q000378:metabolism; D013136:Spiral Ganglion / Q000187:drug effects / Q000502:physiology*; D027981:Symporters / Q000378:metabolism; D000096922:K Cl- Cotransporters
chemical_list: D000075369:Anoctamin-1; D000075368:Anoctamins; D002118:Calcium; D018118:Chloride Channels; D002712:Chlorides; D064506:Solute Carrier Family 12, Member 2; D027981:Symporters; D000096922:K Cl- Cotransporters; C531181:ANO1 protein, mouse; C532161:ANO2 protein, mouse; C578878:Slc12a2 protein, mouse
keywords: action potentials; calcium-activated chloride channels; development; hearing; spiral ganglion neurons