Open AccessNiflumic acid hyperpolarizes smooth muscle cells via calcium‐activated potassium channel in spiral modiolar artery of guinea pigs 1
Author(s) -
LI Li,
MA Ketao,
ZHAO Lei,
SI Junqiang,
ZHANG Zhongshuang,
ZHU He,
LI Jing
Publication year - 2008
Publication title -
acta pharmacologica sinica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.514
H-Index - 90
eISSN - 1745-7254
pISSN - 1671-4083
DOI - 10.1111/j.1745-7254.2008.00803.x
Subject(s) - niflumic acid , apamin , charybdotoxin , iberiotoxin , chemistry , cyclopiazonic acid , hyperpolarization (physics) , ouabain , tetraethylammonium , membrane potential , biophysics , potassium channel , reversal potential , resting potential , potassium , patch clamp , intracellular , biochemistry , stereochemistry , sodium , biology , receptor , organic chemistry , nuclear magnetic resonance spectroscopy
Aim: The influence of niflumic acid (NFA), a Cl − channel antagonist, on the membrane potentials in smooth muscle cells (SMC) of the cochlear spiral modiolar artery (SMA) in guinea pigs was examined. Methods: The intracellular recording and whole‐cell recording technique were used to record the NFA‐induced response on the acutely‐isolated SMA preparation. Results: The SMC had 2 stable but mutually convertible levels of resting potentials (RP), that is, one was near −45 mV and the other was approximately −75 mV, termed as low and high RP, respectively. The bath application of NFA could cause a hyperpolarization in all the low RP cells, but had little effect on high RP cells. The induced responses were concentration‐dependent. Large concentrations of NFA (≥100 μmol/L) often induced a shift of a low RP to high RP in cells with an initial RP at low level, and NFA (up to 100 μmol/L) had little effect on the membrane potentials of the high RP cells. However, when the high RP cells were depolarized to a level beyond −45 mV by barium and ouabain, NFA hyperpolarized these cells with the similar effect on those cells initially being the low RP. The NFA‐induced response was almost completely blocked by charybdotoxin, iberiotoxin, tetraethylammonium, 1,2‐bis (2‐aminophenoxy) ethane‐ N,N,N′,N′ ‐tetraacetic acid tetrakis acetoxymethyl ester, but not by 4‐aminopyridine, barium, glipizide, apamin, ouabain, and CdCl 2 . Conclusion: NFA induces a concentration‐dependent reversible hyperpolarization in SMC in the cochlear SMA via activation of the Ca 2+ ‐activated potassium channels.