Differential regulation of action potentials by inactivating and noninactivating BK channels in rat adrenal chromaffin cells.

Liang Sun, Yu Xiong, Xuhui Zeng, Ying Wu, Na Pan, Christopher J Lingle, Anlian Qu, Jiuping Ding

Key Laboratory of Molecular Biophysics of the Ministry of Education, Huazhong University of Science and Technology, Wuhan, Hubei, China.

Biophysical journal 2009 Oct 7

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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+)].

Citation

Liang Sun, Yu Xiong, Xuhui Zeng, Ying Wu, Na Pan, Christopher J Lingle, Anlian Qu, Jiuping Ding. Differential regulation of action potentials by inactivating and noninactivating BK channels in rat adrenal chromaffin cells. Biophysical journal. 2009 Oct 7;97(7):1832-42