Feature of ACh-sensitive potassium current in outer hair cells of guinea pig cochlea.
- Author:
Chang-kai GUO
1
;
Wei-jia KONG
;
Qing-song YU
;
Guan-qiao LI
;
Jia-li LI
;
Qing-tian LI
Author Information
- Publication Type:Journal Article
- MeSH: Animals; Guinea Pigs; Hair Cells, Auditory, Outer; drug effects; metabolism; Membrane Potentials; Patch-Clamp Techniques; Potassium; metabolism; pharmacology; Potassium Channels; physiology; Receptors, Cholinergic; drug effects; metabolism
- From: Chinese Journal of Otorhinolaryngology Head and Neck Surgery 2007;42(4):286-290
- CountryChina
- Language:Chinese
-
Abstract:
OBJECTIVETo explore the feature of the ACh-sensitive potassium current in guinea pig cochlear outer hair cells.
METHODSCochlear outer hair cells of guinea pigs (n=38) were isolated by collagenase type IV. Under the whole-cell patch mode, the ions nature and the pharmacological properties of the ACh-sensitive potassium current were investigated by applying the inhibitors of calcium-dependent potassium currents and the inhibitors of nicotinic ACh receptor.
RESULTSFollowing application of ACh, cochlear outer hair cells displayed a rapidly activating outward potassium current with a fast desensitized kinetic and a reversal (x +/- s) potential of (-67.3 +/- 8.2) mV (n=10). At the holding potential of -50 mV, the current amplitude of ACh-sensitive potassium current activated by 100 micronmol/L ACh was (506.6 +/- 186.3) pA (n=9). ACh-sensitive potassium current was sensitive to TEA (tetraethylammonium chloride, 10 mmol/L) and potently inhibited by the small conductance calcium-dependent potassium current (SK) blocker, apamin (1 micromol/L). Iberiotoxin (IBTX), the well-known blocker of big conductance calcium-dependent potassium current (BK), failed to inhibit the amplitude of the ACh-sensitive potassium current at the dose of 200 nmol/L. The dose for half-maximal response (EC50) of the ACh-sensitive potassium current was (33.5 +/- 5.7) micromol/L (n=7). The ACh-sensitive potassium current was sensitive to the GABA (gamma-aminobutyric acid)-A receptor blocker, bicuculline, and strongly inhibited by the selective blocker of the alpha 9-nicotinic ACh receptor, strychnine. Strychnine and bicuculline showed the dose-dependent blocking effect with a half inhibition-maximal response (IC50) of (22.3 +/- 2.6) nmol/L (n=7) and (1.2 +/- 0.4) micromol/L (n=6), respectively.
CONCLUSIONSThis work provides direct evidences that the ACh-sensitive SK current was present on guinea pig cochlear outer hair cells. The activation of the ACh-sensitive SK current was most possibly mediated by a alpha 9-nicotinic ACh receptor.