Inward rectifier potassium conductance regulates membrane potential of canine colonic smooth muscle

Flynn, Elaine R. M.; McManus, Ciara A.; Bradley, Karri K.; Koh, Sang Don; Hegarty, Terry M.; Horowitz, Burton; Sanders, Kenton M.

doi:10.1111/j.1469-7793.1999.0247r.x

Cited by 37 publications

(37 citation statements)

References 39 publications

(66 reference statements)

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“…The amplitudes of the currents increased and the reversal potentials were altered by elevating the external K + concentration, demonstrating that the properties of these channels resemble those of inward rectifier K + currents. In particular, the voltagedependent block by Ba 2+ or Cs + is quite similar to those reported earlier (Flynn et al, 1999;Thompson et al, 2000;Murata et al, 2002), which indicated that this hyperpolarization-activated current was an inward rectifier K Other currents that may activate in these voltage ranges include the hyperpolarizationactivated nonselective cation current and the HERG current. However, HERG channels would typically be closed at holding potentials negative to 80 mV, and the activation kinetics and Ba 2+ sensitivity did not match well with the properties of hyperpolarization-activated nonselective cation currents.…”

Section: Discussionsupporting

confidence: 67%

Characterization of Ionic Currents in Human Neural Stem Cells

Lim

Kim

Suh‐Kim

et al. 2008

Korean J Physiol Pharmacol

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The profile of membrane currents was investigated in differentiated neuronal cells derived from human neural stem cells (hNSCs) that were obtained from aborted fetal cortex. W hole-cell voltage clamp recording revealed at least 4 different currents: a tetrodotoxin (TTX)-sensitive Na + current, a hyperpolarization-activated inward current, and A-type and delayed rectifier-type K + outward currents. Both types of K + outward currents were blocked by either 5 mM tetraethylammonium (TEA) or 5 mM 4-aminopyridine (4-AP). The hyperpolarization-activated current resembled the classical K + inward current in that it exhibited a voltage-dependent block in the presence of external Ba 2+ (30μ M) or Cs + (3μ M). However, the reversal potentials did not match well with the predicted K + equilibrium potentials, suggesting that it was not a classical K + inward rectifier current. The other Na + inward current resembled the classical Na + current observed in pharmacological studies. The expression of these channels may contribute to generation and repolarization of action potential and might be regarded as functional markers for hNSCs-derived neurons.

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Section: Discussionsupporting

confidence: 67%

Characterization of Ionic Currents in Human Neural Stem Cells

Lim

Kim

Suh‐Kim

et al. 2008

Korean J Physiol Pharmacol

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“…The RT-PCR analysis demonstrated the presence of Kir2.1 but not Kir2.2 and Kir2.3 in rat cerebral, coronary and mesenteric artery, canine colonic smooth muscle, and human bronchial smooth muscle Oonuma et al, 2002;Flynn et al, 1999), although Kir2.4 was not examined in these studies.…”

Section: Introductionmentioning

confidence: 80%

Functional Expression of Inward Rectifier Potassium Channels in Cultured Human Pulmonary Smooth Muscle Cells: Evidence for a Major Role of Kir2.4 Subunits

2006

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“…A window current via this conductance contributes to E m between slow waves in murine antral tissue, but when this current was blocked, changes in spontaneous slow-wave shape were not evident (1). Inward rectifier K ϩ channels are found in canine colonic circular smooth muscle and may be predominantly located in ICC (8), but little inward rectifier current passes at depolarized potentials. In rat fundus, a transient Na ϩ current inactivates within a few milliseconds (33).…”

Section: Discussionmentioning

confidence: 99%

Mathematical description of regenerative potentials recorded from circular smooth muscle of guinea pig antrum

Edwards

Hirst

2003

American Journal of Physiology-Gastrointestinal and Liver Physi

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tentials evoked by intracellular current injection in single bundles of circular smooth muscle taken from guinea pig antrum have the characteristics of the secondary regenerative component of the slow wave occurring in the same muscle layer. Such regenerative depolarizations might result from a mechanism that responds to membrane polarization with a delayed increase in the rate of production of unitary potentials detected in this tissue. To test this possibility, a two-stage reaction leading to the formation of an intracellular messenger was proposed. The first forward reaction was voltage-dependent, in the manner described by the HodgkinHuxley transient Na conductance formalism, allowing simulation of anode break excitation, stimulus threshold strength-duration characteristics, and refractory behavior. A conventional dose-effect relationship was proposed to describe the dependence of the mean rate of discharge of unitary potentials on messenger concentration. Unitary potentials were modeled as unitary membrane conductance modulations with an empirically derived amplitude distribution and Poisson-distributed intervals. The model reproduces a range of spontaneous and evoked membrane potential changes characteristic of antral circular muscle bundles. mathematical model; stomach; slow wave; interstitial cells of Cajal; inositol 1,4,5-trisphosphate MOST REGIONS OF THE GASTROINTESTINAL tract generate rhythmic contractions in the absence of neuronal or hormonal stimulation. Each contraction is associated with a wave of depolarization called a slow wave (25,30). In the guinea pig gastric antrum, slow waves are initiated by pacemaker potentials generated in myenteric interstitial cells of Cajal (ICC MY ) (5). Waves of pacemaker depolarization spread passively to the longitudinal and circular muscle layers. In the circular muscle layer, the waves of depolarization initiate the secondary regenerative component of the slow wave (5). The secondary component is dependent on the presence of intramuscular ICC (ICC IM ), which is absent in the gastric antrum of mutant mice that lack this population of cells (4).Regenerative potentials that share the characteristics of the secondary component of the slow wave can be initiated in isolated individual bundles of circular muscle (6, 28). Preparations were impaled with two intracellular electrodes, with one electrode to pass depolarizing current pulses and the other to record membrane potential (E m ) changes. Depolarization evoked a regenerative response with a minimum latency of ϳ1 s (28). The repolarizing step, ending a period of membrane hyperpolarization, also evoked a regenerative response but with a longer minimum latency of ϳ2.5 s (28). Regenerative responses appear to depend on the release of Ca 2ϩ from intracellular stores followed by the activation of anion-selective ion channels (13). They are abolished by depleting internal Ca 2ϩ stores (28), by buffering the cytosolic free Ca 2ϩ concentration, [Ca 2ϩ ] i to low levels (6), and by 2-APB (9, 13, 14), an agent that preve...

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Inward rectifier potassium conductance regulates membrane potential of canine colonic smooth muscle

Cited by 37 publications

References 39 publications

Characterization of Ionic Currents in Human Neural Stem Cells

Characterization of Ionic Currents in Human Neural Stem Cells

Functional Expression of Inward Rectifier Potassium Channels in Cultured Human Pulmonary Smooth Muscle Cells: Evidence for a Major Role of Kir2.4 Subunits

Mathematical description of regenerative potentials recorded from circular smooth muscle of guinea pig antrum

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