Apamin-sensitive, small-conductance, calcium-activated potassium channels mediate cholinergic inhibition of chick auditory hair cells |
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| Authors: | W A Yuhas P A Fuchs |
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| Institution: | (1) Department of Cell and Structural Biology, University of Colorado Health Sciences Center, Box B-111, 4200 E. Ninth Ave., Denver, CO 80262 e-mail: ward.yuhas@uchsc.edu Tel.: +1-303-315-8547; Fax: +1-303-315-4729, US;(2) Center for Hearing Sciences, Departments of Otolaryngology-HNS and Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA e-mail: pfuchs@bme.jhu.edu Tel.: +1-410-955-6311; Fax: +1-410-614-4748, US |
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| Abstract: | Acetylcholine released from efferent neurons in the cochlea causes inhibition of mechanosensory hair cells due to the activation
of calcium-dependent potassium channels. Hair cells are known to have large-conductance, “BK”-type potassium channels associated
with the afferent synapse, but these channels have different properties than those activated by acetylcholine. Whole-cell (tight-seal) and
cell-attached patch-clamp recordings were made from short (outer) hair cells isolated from the chicken basilar papilla (cochlea
equivalent). The peptides apamin and charybdotoxin were used to distinguish the calcium-activated potassium channels involved
in the acetylcholine response from the BK-type channels associated with the afferent synapse. Differential toxin blockade
of these potassium currents provides definitive evidence that ACh activates apamin-sensitive, “SK”-type potassium channels,
but does not activate carybdotoxin-sensitive BK channels. This conclusion is supported by tentative identification of small-conductance,
calcium-sensitive but voltage-insensitive potassium channels in cell-attached patches. The distinction between these channel
types is important for understanding the segregation of opposing afferent and efferent synaptic activity in the hair cell,
both of which depend on calcium influx. These different calcium-activated potassium channels serve as sensitive indicators
for functionally significant calcium influx in the hair cell.
Accepted: 12 August 1999 |
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| Keywords: | Apamin BK Charybdotoxin Cochlea SK |
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