Premium
Heterogeneous expression of transient outward currents in smooth muscle cells of the mouse small intestine
Author(s) -
Lee Jonathan C. F.,
BarajasLópez Carlos,
Huizinga Jan D.
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2001.013557
Subject(s) - depolarization , conductance , chemistry , biophysics , membrane potential , chord (peer to peer) , physics , biology , biochemistry , condensed matter physics , distributed computing , computer science
The objective for this paper was to characterize the transient outward current ( I to ) present in smooth muscle cells of the intestinal external muscularis. Two populations of cells were identified, one with a fast rate of I to inactivation (τ < 100 ms) and another with a slow rate of I to inactivating (τ > 150 ms). The chord conductance for the fast I to was smaller than the chord conductance of the slow I to (0.5 ± 0.1 vs. 1.3 ± 0.1 nS pF −1 , respectively). The inactivation was fitted by mono‐exponentials to give a τ for the fast and slow I to of 44 and 229 ms, respectively. Combined plots of voltage dependent activation and inactivation processes revealed voltage ranges where window currents were possible; a 20 mV range for the fast I to from −56 to −36 mV and a 47 mV range for the slow I to from −42 to +5 mV. The fast I to recovered more quickly from inactivation than the slow I to ; τ(fast I to ) = 11 ± 4 ms compared to τ(slow I to ) = 42 ± 16 ms. The effect of different rates of depolarization on I to activation was examined. The plots of peak currents evoked by different rates of depolarization were well fitted by inverse exponential functions. The fast I to had a larger response to fast rates of depolarization by having a τ of 2 ± 1 mV ms −1 with maximal activation (95 % complete) at 5 mV ms −1 . The slow I to had a τ of 14 ± 9 mV ms −1 with maximal activation (95 % complete) at 42 mV ms −1 . The properties of these currents suggest that the two transient outward currents may contribute differently to slow waves and action potentials generated by the smooth muscle cells.