Properties of ACh-sensitive BK channels in mice type Ⅱ vestibular hair cells and its modulation by calcium / 中国病理生理杂志

ABSTRACT

AIM: To explore the properties of the acetylcholine(ACh)-sensitive potassium channel in type Ⅱ vestibular hair cells(VHCs Ⅱ) in mice saccular macula and the modulation effect of calcium ions.METHODS: Under the whole-cell patch mode,the pharmacology properties of ACh-sensitive potassium channel and the modulation of calcium ions on ACh-sensitive potassium channel were investigated.RESULTS: Following extracellular perfusion of ACh,VHCs Ⅱ displayed a slow and sustained outward current,which was sensitive to tetraethylammonium(TEA,5 mmol/L) and charybdotoxin(CTX,100 nmol/L),but not sensitive to 4-aminopyride(4-AP,15 ?mol/L).ACh-sensitive potassium current was inhibited by intracellular application of ethylene glycol-bis(B-aminoethylether)-N,N,N',N'-tetraacetic-acid(EGTA,5 mmol/L) and extracellular perfusion of Cd2+ and Ni2+,respectively.Intracellular application of heparin(8 g/L) failed to inhibit ACh-sensitive potassium current.CONCLUSION: Extracellular application of ACh activates the big conductance,calcium-dependent potassium current(BK) in VHCs Ⅱ of mice,which is potently modulated by extracellular Ca2+ ions.However,intracellular IP3-dependent Ca2+ ions release mechanism is not involved in the activation of the ACh-sensitive BK channel.