The role of K⁺ conductances in regulating membrane excitability in human gastric corpus smooth muscle.
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.
Affiliation: Samsung Biomedical Research Institute and.Show MeSH
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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.