scholarly journals Differential Regulation of Action Potentials by Inactivating and Noninactivating BK Channels in Rat Adrenal Chromaffin Cells

2009 ◽  
Vol 97 (7) ◽  
pp. 1832-1842 ◽  
Author(s):  
Liang Sun ◽  
Yu Xiong ◽  
Xuhui Zeng ◽  
Ying Wu ◽  
Na Pan ◽  
...  
Keyword(s):  
Action Potentials ◽  
Chromaffin Cells ◽  
Bk Channels ◽  
Differential Regulation ◽  
Adrenal Chromaffin Cells ◽  
Adrenal Chromaffin

Inward currents underlying action potentials in rat adrenal chromaffin cells

1996 ◽  
Vol 76 (2) ◽  
pp. 1195-1211 ◽  
Author(s):  
B. Hollins ◽  
S. R. Ikeda
Keyword(s):  
Ion Channels ◽  
Voltage Clamp ◽  
Action Potentials ◽  
Chromaffin Cells ◽  
Na Channels ◽  
Adrenal Chromaffin Cells ◽  
Voltage Dependent ◽  
Slope Factor ◽  
Inward Currents ◽  
Adrenal Chromaffin

1. Current- and voltage-clamp studies were conducted on isolated rat adrenal chromaffin cells to identify the voltage-dependent ion channels mediating inward currents. 2. Mean resting membrane potential of the isolated cells was -62 +/- 3 (SE) mV. Evoked action potentials were both Na+ and Ca2+ based, and whole cell voltage-clamp studies in normal saline revealed an inward-rectifier-type current. 3. Na+ channels were studied in isolation and showed a half-inactivation of -60 +/- 2 mV with a slope factor of -6 mV and a half-activation of -26.8 +/- 2 mV with a slope factor of 6.5 +/- 0.7 mV. 4. Isolated Ca2+ currents, elicited in 10 mM external Ca2+, revealed a T-type current in a subset of cells. Ca2+ currents were sensitive to both N- and L-type channel antagonists, and blockade of the current by the L-type channel antagonist nimodipine and the N-type channel antagonist omega-conotoxin GVIA revealed a third Ca2+-current component that was unaffected by the P-type channel antagonist omega-agatoxin IVA. 5. Ca2+ currents were facilitated 5-20% by a depolarizing prepulse, and facilitation was completely blocked by nimodipine. The effects of the dihydropyridine L-type channel agonist, (+)202-791 and depolarizing prepulses on the currents were additive. 6. The results of this study show that the properties of voltage-dependent ion channels in rat chromaffin cells differ from those reported in their counterparts in bovine chromaffin cells. Na+ channels differ in activation and inactivation properties and Ca2+ channels differ in activation, sensitivity to antagonists, and the magnitude of voltage-dependent facilitation.

Bovine Versus Rat Adrenal Chromaffin Cells: Big Differences in BK Potassium Channel Properties

2000 ◽  
Vol 83 (6) ◽  
pp. 3277-3286 ◽  
Author(s):  
Peter V. Lovell ◽  
Dustin G. James ◽  
David P. McCobb
Keyword(s):  
Stress Responses ◽  
Chromaffin Cells ◽  
Outward Current ◽  
Bk Channels ◽  
Bk Channel ◽  
Model Systems ◽  
Adrenal Chromaffin Cells ◽  
Current Profile ◽  
Species Specific ◽  
Adrenal Chromaffin

Both bovine and rat adrenal chromaffin cells have served as pioneering model systems in cellular neurophysiology, including in the study of large conductance calcium- and voltage-dependent K+ (BK) channels. We now report that while BK channels dominate the outward current profile of both species, specific gating properties vary widely across cell populations, and the distributions of these properties differ dramatically between species. Although BK channels were first described in bovine chromaffin cells, rapidly inactivating ones were discovered in rat chromaffin cells. We report that bovine cells can also exhibit inactivating BK channels with varying properties similar to those in rat cells. However, a much smaller proportion of bovine cells exhibit inactivating BK current, the proportion of the total current that inactivates is usually smaller, and the rate of inactivation is often much slower. Other gating features differ as well; the voltage dependence of channel activation is much more positive for bovine cells, and their rates of activation and deactivation are faster and slower, respectively. Modeling studies suggest that channel heterogeneity is consistent with varying tetrameric combinations of inactivation-competent versus -incompetent subunits. The results suggest that chromaffin BK channel functional nuances represent an important level for evolutionary tailoring of autonomic stress responses.

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