Feature of ACh-sensitive potassium current in outer hair cells of guinea pig cochlea / 中华耳鼻咽喉头颈外科杂志
Chinese Journal of Otorhinolaryngology Head and Neck Surgery
;
(12): 286-290, 2007.
Article
in Chinese
| WPRIM
| ID: wpr-262884
ABSTRACT
<p><b>OBJECTIVE</b>To explore the feature of the ACh-sensitive potassium current in guinea pig cochlear outer hair cells.</p><p><b>METHODS</b>Cochlear 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.</p><p><b>RESULTS</b>Following 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.</p><p><b>CONCLUSIONS</b>This 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.</p>
Full text:
Available
Index:
WPRIM (Western Pacific)
Main subject:
Pharmacology
/
Physiology
/
Potassium
/
Potassium Channels
/
Receptors, Cholinergic
/
Hair Cells, Auditory, Outer
/
Patch-Clamp Techniques
/
Guinea Pigs
/
Membrane Potentials
/
Metabolism
Limits:
Animals
Language:
Chinese
Journal:
Chinese Journal of Otorhinolaryngology Head and Neck Surgery
Year:
2007
Type:
Article
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