• KSBNS 2024


Original Article

Exp Neurobiol 2022; 31(4): 243-259

Published online August 31, 2022

© The Korean Society for Brain and Neural Sciences

Low-voltage Activating K+ Channels in Cochlear Afferent Nerve Fiber Dendrites

Kushal Sharma1, Kwon Woo Kang1, Young-Woo Seo2, Elisabeth Glowatzki3 and Eunyoung Yi1*

1College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, 2KBSI Gwangju Center, Korea Basic Science Institute, Gwangju 61186, Korea, 3Department of Otolaryngology-Head and Neck Surgery and Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA

Correspondence to: *To whom correspondence should be addressed.
TEL: 82-61-450-2683, FAX: 82-61-450-2689

Received: April 1, 2022; Revised: June 18, 2022; Accepted: July 29, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Cochlear afferent nerve fibers (ANF) are the first neurons in the ascending auditory pathway. We investigated the low-voltage activating K+ channels expressed in ANF dendrites using isolated rat cochlear segments. Whole cell patch clamp recordings were made from the dendritic terminals of ANFs. Outward currents activating at membrane potentials as low as -64 mV were observed in all dendrites studied. These currents were inhibited by 4-aminopyridine (4-AP), a blocker known to preferentially inhibit low-voltage activating K+ currents (IKL) in CNS auditory neurons and spiral ganglion neurons. When the dendritic IKL was blocked by 4-AP, the EPSP decay time was significantly prolonged, suggesting that dendritic IKL speeds up the decay of EPSPs and likely modulates action potentials of ANFs. To reveal molecular subtype of dendritic IKL, α-dendrotoxin (α-DTX), a selective inhibitor for Kv1.1, Kv1.2, and Kv1.6 containing channels, was tested. α-DTX inhibited 23±9% of dendritic IKL. To identify the α-DTXsensitive and α-DTX-insensitive components of IKL, immunofluorescence labeling was performed. Strong Kv1.1- and Kv1.2-immunoreactivity was found at unmyelinated dendritic segments, nodes of Ranvier, and cell bodies of most ANFs. A small fraction of ANF dendrites showed Kv7.2- immunoreactivity. These data suggest that dendritic IKL is conducted through Kv1.1and Kv1.2 channels, with a minor contribution from Kv7.2 and other as yet unidentified channels.

Graphical Abstract

Keywords: Cochlea, Kv1.1, Kv1.2, Auditory nerve fiber, Hair cell, Ribbon synapse