Differential regulation of action potentials by inactivating and noninactivating BK channels in rat adrenal chromaffin cells.
Large-conductance Ca(2+)-activated K(+) (BK) channels can regulate cellular excitability in complex ways because they are able to respond independently to two distinct cellular signals, cytosolic Ca(2+) and membrane potential. In rat chromaffin cells (RCC), inactivating BK(i) and noninactivating (BK(s)) channels differentially contribute to RCC action potential (AP) firing behavior. However, the basis for these differential effects has not been fully established. Here, we have simulated RCC action potential behavior, using Markovian models of BK(i) and BK(s) current and other RCC currents. The analysis shows that BK current influences both fast hyperpolarization and afterhyperpolarization of single APs and that, consistent with experimental observations, BK(i) current facilitates repetitive firing of APs, whereas BK(s) current does not. However, the key functional difference between BK(i) and BK(s) current that accounts for the differential firing is not inactivation but the more negatively shifted activation range for BK(i) current at a given [Ca(2+)].
Key Laboratory of Molecular Biophysics of the Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, China.
Liang
L
Sun
Yu
Y
Xiong
Xuhui
X
Zeng
Ying
Y
Wu
Na
N
Pan
Christopher J
CJ
Lingle
Anlian
A
Qu
Jiuping
J
Ding
D000200:Action Potentials; D000313:Adrenal Medulla / Q000166:cytology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D019439:Chromaffin Cells / Q000166:cytology* / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004553:Electric Conductivity; D007700:Kinetics; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D008954:Models, Biological; D024642:Potassium Channels, Voltage-Gated / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism
D051036:Large-Conductance Calcium-Activated Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012964:Sodium; D002118:Calcium