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The role of K⁺ conductances in regulating membrane excitability in human gastric corpus smooth muscle.

Lee JY, Ko EJ, Ahn KD, Kim S, Rhee PL - Am. J. Physiol. Gastrointest. Liver Physiol. (2015)

Bottom Line: Tetraethylammonium and charybdotoxin did not affect the RMP, suggesting that BK channels are not involved in regulating RMP.Apamin, a selective small conductance Ca(2+)-activated K(+) channel (SK) blocker, did not show a significant effect on the membrane excitability. 4-Aminopyridine, a Kv channel blocker, caused depolarization and increased the duration of slow wave potentials. 4-Aminopyridine also inhibited a delayed rectifying K(+) current in isolated smooth muscle cells.Glibenclamide, an ATP-sensitive K(+) channel (KATP) blocker, did not induce depolarization, but nicorandil, a KATP opener, hyperpolarized HGCS, suggesting that KATP are expressed but not basally activated.

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Affiliation: Samsung Biomedical Research Institute and.

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Effect of TEA, 4-AP, and Ba2+ on the outward currents in isolated HGCS cells. A and B: a representative trace showed outward currents during ramp depolarization (from −80 to +80 mV; see inset) from a holding potential of −80 mV. TEA (10 mM) did not show significant effect on evoked outward currents (A). However, 4-AP (5 mM) decreased the outward currents (B). C: a representative trace showed the effect of Ba2+ (100 μM) after replacement with K+-rich solution (HK; see methods) at −80 mV. Vertical lines denote ramp depolarization and blue dotted line denotes the holding current at −80 mV. D: a (black line) and b (red line) are evoked currents during ramp depolarization from C in control and HK presence, respectively. E: bath application of Ba2+ (100 μM, c: green line) under external K+-rich solution (b: red line) at a holding potential of −80 mV did not reveal significant effect on ramp-evoked currents.
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Figure 8: Effect of TEA, 4-AP, and Ba2+ on the outward currents in isolated HGCS cells. A and B: a representative trace showed outward currents during ramp depolarization (from −80 to +80 mV; see inset) from a holding potential of −80 mV. TEA (10 mM) did not show significant effect on evoked outward currents (A). However, 4-AP (5 mM) decreased the outward currents (B). C: a representative trace showed the effect of Ba2+ (100 μM) after replacement with K+-rich solution (HK; see methods) at −80 mV. Vertical lines denote ramp depolarization and blue dotted line denotes the holding current at −80 mV. D: a (black line) and b (red line) are evoked currents during ramp depolarization from C in control and HK presence, respectively. E: bath application of Ba2+ (100 μM, c: green line) under external K+-rich solution (b: red line) at a holding potential of −80 mV did not reveal significant effect on ramp-evoked currents.

Mentions: Since the most prominent findings by microelectrode recordings in HGCS are 4-AP and Ba2+ sensitive, we performed patch-clamp experiments to characterize the 4-AP and Ba2+-sensitive currents from isolated smooth muscle cells of the HGCS. Whole-cell voltage-clamp techniques were employed. The external solution was MnPSS (see methods) with dialyzed K+-rich solution (10 mM BAPTA to prevent the contamination of Ca2+-activated K+ currents; see methods). Ramp depolarization to +80 mV from a holding potential of −80 mV was applied (see insets in Fig. 8, A and B). A high concentration of TEA (10 mM) had no effect on the evoked currents (Fig. 8A, n = 5), but 4-AP (5 mM) inhibited outward currents from 158 ± 12 pA to 68 ± 6 pA at 0 mV (Fig. 7B, P < 0.01, n = 6). These data suggest that HGCS smooth muscle cells express 4-AP-sensitive Kv currents.


The role of K⁺ conductances in regulating membrane excitability in human gastric corpus smooth muscle.

Lee JY, Ko EJ, Ahn KD, Kim S, Rhee PL - Am. J. Physiol. Gastrointest. Liver Physiol. (2015)

Effect of TEA, 4-AP, and Ba2+ on the outward currents in isolated HGCS cells. A and B: a representative trace showed outward currents during ramp depolarization (from −80 to +80 mV; see inset) from a holding potential of −80 mV. TEA (10 mM) did not show significant effect on evoked outward currents (A). However, 4-AP (5 mM) decreased the outward currents (B). C: a representative trace showed the effect of Ba2+ (100 μM) after replacement with K+-rich solution (HK; see methods) at −80 mV. Vertical lines denote ramp depolarization and blue dotted line denotes the holding current at −80 mV. D: a (black line) and b (red line) are evoked currents during ramp depolarization from C in control and HK presence, respectively. E: bath application of Ba2+ (100 μM, c: green line) under external K+-rich solution (b: red line) at a holding potential of −80 mV did not reveal significant effect on ramp-evoked currents.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385896&req=5

Figure 8: Effect of TEA, 4-AP, and Ba2+ on the outward currents in isolated HGCS cells. A and B: a representative trace showed outward currents during ramp depolarization (from −80 to +80 mV; see inset) from a holding potential of −80 mV. TEA (10 mM) did not show significant effect on evoked outward currents (A). However, 4-AP (5 mM) decreased the outward currents (B). C: a representative trace showed the effect of Ba2+ (100 μM) after replacement with K+-rich solution (HK; see methods) at −80 mV. Vertical lines denote ramp depolarization and blue dotted line denotes the holding current at −80 mV. D: a (black line) and b (red line) are evoked currents during ramp depolarization from C in control and HK presence, respectively. E: bath application of Ba2+ (100 μM, c: green line) under external K+-rich solution (b: red line) at a holding potential of −80 mV did not reveal significant effect on ramp-evoked currents.
Mentions: Since the most prominent findings by microelectrode recordings in HGCS are 4-AP and Ba2+ sensitive, we performed patch-clamp experiments to characterize the 4-AP and Ba2+-sensitive currents from isolated smooth muscle cells of the HGCS. Whole-cell voltage-clamp techniques were employed. The external solution was MnPSS (see methods) with dialyzed K+-rich solution (10 mM BAPTA to prevent the contamination of Ca2+-activated K+ currents; see methods). Ramp depolarization to +80 mV from a holding potential of −80 mV was applied (see insets in Fig. 8, A and B). A high concentration of TEA (10 mM) had no effect on the evoked currents (Fig. 8A, n = 5), but 4-AP (5 mM) inhibited outward currents from 158 ± 12 pA to 68 ± 6 pA at 0 mV (Fig. 7B, P < 0.01, n = 6). These data suggest that HGCS smooth muscle cells express 4-AP-sensitive Kv currents.

Bottom Line: Tetraethylammonium and charybdotoxin did not affect the RMP, suggesting that BK channels are not involved in regulating RMP.Apamin, a selective small conductance Ca(2+)-activated K(+) channel (SK) blocker, did not show a significant effect on the membrane excitability. 4-Aminopyridine, a Kv channel blocker, caused depolarization and increased the duration of slow wave potentials. 4-Aminopyridine also inhibited a delayed rectifying K(+) current in isolated smooth muscle cells.Glibenclamide, an ATP-sensitive K(+) channel (KATP) blocker, did not induce depolarization, but nicorandil, a KATP opener, hyperpolarized HGCS, suggesting that KATP are expressed but not basally activated.

View Article: PubMed Central - PubMed

Affiliation: Samsung Biomedical Research Institute and.

Show MeSH
Related in: MedlinePlus