Characterization of calcium-activated potassium channels in single smooth muscle cells using the patch-clamp technique

1987 ◽  
Vol 408 (2) ◽  
pp. 98-111 ◽  
Author(s):  
Joshua J. Singer ◽  
V. Walsh
Keyword(s):  
Smooth Muscle ◽  
Potassium Channels ◽  
Patch Clamp ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Patch Clamp Technique ◽  
Clamp Technique ◽  
Calcium Activated Potassium Channels

Ketamine blocks Ca2+-activated K+ channels in rabbit cerebral arterial smooth muscle cells

2003 ◽  
Vol 285 (3) ◽  
pp. H1347-H1355 ◽  
Author(s):  
Jin Han ◽  
Nari Kim ◽  
Hyun Joo ◽  
Euiyong Kim
Keyword(s):  
Smooth Muscle ◽  
Patch Clamp ◽  
Smooth Muscle Cells ◽  
Cerebral Arteries ◽  
Muscle Cells ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Arterial Smooth Muscle ◽  
Clamp Technique ◽  
Arterial Smooth Muscle Cells

Although ketamine and Ca2+-activated K+ (KCa) channels have been implicated in the contractile activity regulation of cerebral arteries, no studies have addressed the specific interactions between ketamine and the KCa channels in cerebral arteries. The purpose of this study was to examine the direct effects of ketamine on KCa channel activities using the patch-clamp technique in single-cell preparations of rabbit middle cerebral arterial smooth muscle. We tested the hypothesis that ketamine modulates the KCa channel activity of the cerebral arterial smooth muscle cells of the rabbit. Vascular myocytes were isolated from rabbit middle cerebral arteries using enzymatic dissociation. Single KCa channel activities of smooth muscle cells from rabbit cerebral arteries were recorded using the patch-clamp technique. In the inside-out patches, ketamine in the micromolar range inhibited channel activity with a half-maximal inhibition of the ketamine conentration value of 83.8 ± 12.9 μM. The Hill coefficient was 1.2 ± 0.3. The slope conductance of the current-voltage relationship was 320.1 ± 2.0 pS between 0 and +60 mV in the presence of ketamine and symmetrical 145 mM K+. Ketamine had little effect on either the voltage-dependency or open- and closed-time histograms of KCa channel. The present study clearly demonstrates that ketamine inhibits KCa channel activities in rabbit middle cerebral arterial smooth muscle cells. This inhibition of KCa channels may represent a mechanism for ketamine-induced cerebral vasoconstriction.

Effects of the gap junction blocker glycyrrhetinic acid on gastrointestinal smooth muscle cells

2005 ◽  
Vol 288 (4) ◽  
pp. G832-G841 ◽  
Author(s):  
Yukari Takeda ◽  
Sean M. Ward ◽  
Kenton M. Sanders ◽  
Sang Don Koh
Keyword(s):  
Smooth Muscle ◽  
Patch Clamp ◽  
Smooth Muscle Cells ◽  
Gap Junctions ◽  
Lucifer Yellow ◽  
Muscle Cells ◽  
Glycyrrhetinic Acid ◽  
Delayed Rectifier ◽  
Dependent Manner ◽  
Patch Clamp Technique

In the tunica muscularis of the gastrointestinal (GI) tract, gap junctions form low-resistance pathways between pacemaker cells known as interstitial cells of Cajal (ICCs) and between ICC and smooth muscle cells. Coupling via these junctions facilitates electrical slow-wave propagation and responses of smooth muscle to enteric motor nerves. Glycyrrhetinic acid (GA) has been shown to uncouple gap junctions, but previous studies have shown apparent nonspecific effects of GA in a variety of tissues. We tested the effects of GA using isometric force measurements, intracellular microelectrode recordings, the patch-clamp technique, and the spread of Lucifer yellow within cultured ICC networks. In murine small intestinal muscles, β-GA (10 μM) decreased phasic contractions and depolarized resting membrane potential. Preincubation of GA inhibited the spread of Lucifer yellow, increased input resistance, and decreased cell capacitance in ICC networks, suggesting that GA uncoupled ICCs. In patch-clamp experiments of isolated jejunal myocytes, GA significantly decreased L-type Ca2+ current in a dose-dependent manner without affecting the voltage dependence of this current. The IC50 for Ca2+ currents was 1.9 μM, which is lower than the concentrations used to block gap junctions. GA also significantly increased large-conductance Ca2+-activated K+ currents but decreased net delayed rectifier K+ currents, including 4-aminopyridine and tetraethylammonium-resistant currents. In conclusion, the reduction of phasic contractile activity of GI muscles by GA is likely a consequence of its inhibitory effects on gap junctions and voltage-dependent Ca2+ currents. Membrane depolarization may be a consequence of uncoupling effects of GA on gap junctions between ICCs and smooth muscles and inhibition of K+ conductances in smooth muscle cells.

ATP-sensitive K+ currents in cerebral arterial smooth muscle: pharmacological and hormonal modulation

1995 ◽  
Vol 269 (5) ◽  
pp. H1634-H1640 ◽  
Author(s):  
T. Kleppisch ◽  
M. T. Nelson
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Cerebral Arteries ◽  
Katp Channels ◽  
Muscle Cells ◽  
Patch Clamp Technique ◽  
Calcitonin Gene ◽  
Hormonal Modulation ◽  
Calcium Activated Potassium Channels ◽  
Induced Currents

Calcitonin gene-related peptide (CGRP), hypoxia, and synthetic activators of ATP-sensitive potassium (KATP) channels (e.g., pinacidil and levcromakalim) cause dilation of cerebral arteries that are attenuated by the KATP channel inhibitor glibenclamide. We have identified and characterized KATP currents in smooth muscle cells isolated from rabbit cerebral arteries, using the whole cell configuration of the patch-clamp technique. Pinacidil (10 microM) and levcromakalim (10 microM) increased glibenclamide-sensitive currents about sixfold in cells dialyzed with 0.1 mM ATP. Glibenclamide-sensitive currents in the presence of pinacidil were potassium selective, voltage independent, and reduced about threefold by elevating intracellular ATP from 0.1 to 3.0 mM. External tetraethylammonium and 4-aminopyridine at millimolar concentrations reduced pinacidil-induced currents, whereas iberiotoxin, a blocker of calcium-activated potassium channels, had no effect. The vasoconstrictors serotonin and histamine also inhibited pinacidil-induced currents. The vasodilators CGRP and adenosine, in contrast, increased glibenclamide-sensitive potassium currents. We conclude that cerebral artery smooth muscle cells have KATP channels that are regulated by endogenous vasoconstrictors and vasodilators. We propose that these channels are involved in the dilation of cerebral arteries to CGRP and synthetic vasodilators.

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