[Co-location of ACh-sensitive BK channels and L-type calcium channels in type II vestibular hair cells of guinea pig].
OBJECTIVE
To explore the mechanisms of the influx of calcium ions during the activation of ACh-sensitive BK channel (big conductance, calcium-dependent potassium channel) in type II vestibular hair cells of guinea pigs.


METHODS
Type II vestibular hair cells were isolated by collagenase type IA. Under the whole-cell patch mode, the sensitivity of ACh-sensitive BK current to the calcium channels blockers was investigated, the pharmacological property of L-type calcium channel activator-sensitive current and ACh-sensitive BK current was compared.


RESULTS
Following application of ACh, type II vestibular hair cells displayed a sustained outward potassium current, with a reversal potential of (-70.5 +/- 10.6) mV (x +/- s, n = 10). At the holding potential of -50 mV, the current amplitude of ACh-sensitive potassium current activated by 100 micromol/L ACh was (267 +/- 106) pA (n = 11). ACh-sensitive potassium current was potently sensitive to the BK current blocker, IBTX (iberiotoxin, 200 nmol/L). Apamin, the well-known small conductance, calcium-dependent potassium current blocker, failed to inhibit the amplitude of ACh-sensitive potassium current at a dose of 1 micromol/L. ACh-sensitive BK current was sensitive to NiCl2 and potently inhibited by CdCl2. NiCl2 and CdCl2 showed a dose-dependent blocking effect with a half inhibition-maximal response of (135.5 +/- 18.5) micromol/L (n = 7) and (23.4 +/- 2.6) micromol/L (n = 7). The L-type calcium channel activator, (-) -Bay-K 8644 (10 micromol /L), mimicked the role of ACh and activated the IBTX-sensitive outward current.


CONCLUSIONS
ACh-sensitive BK and L-type calcium channels are co-located in type II vestibular hair cells of guinea pigs.
Guo
Chang-Kai
CK
Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
Li
Guan-Qiao
GQ
Kong
Wei-Jia
WJ
Zhang
Song
S
Wu
Ting-Ting
TT
Li
Jia-Li
JL
Li
Qing-Tian
QT
D000818:Animals; D020746:Calcium Channels, L-Type; D006168:Guinea Pigs; D018069:Hair Cells, Vestibular / Q000378:metabolism*; D051036:Large-Conductance Calcium-Activated Potassium Channels; D018408:Patch-Clamp Techniques
D020746:Calcium Channels, L-Type; D051036:Large-Conductance Calcium-Activated Potassium Channels