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Related Concept Videos

Voltage-gated Ion Channels01:26

Voltage-gated Ion Channels

Voltage-gated ion channels are transmembrane proteins that open and close in response to changes in the membrane potential. They are present on the membranes of all electrically excitable cells such as neurons, heart, and muscle cells.
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
Voltage-gated Ion Channels01:26

Voltage-gated Ion Channels

Voltage-gated ion channels are transmembrane proteins that open and close in response to changes in the membrane potential. They are present on the membranes of all electrically excitable cells such as neurons, heart, and muscle cells.
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
pH Regulation in Cells01:28

pH Regulation in Cells

pH plays a critical role in maintaining normal cellular activities. It helps maintain the structure and function of various proteins, dictates the charge on cellular membranes, and is crucial for metabolic reactions inside the cell. Moreover, cells use the energy from the proton motive force to generate ATP.
Cytosolic pH
Under physiological conditions, the cytosolic pH is slightly more acidic than the extracellular pH. However, cells must prevent further acidification of their cytosol to...
Regulation of Sodium and Potassium01:26

Regulation of Sodium and Potassium

The regulation of sodium and potassium ion concentrations in the human body is a complex process governed primarily by hormones such as aldosterone, antidiuretic hormone (ADH), and atrial natriuretic peptide (ANP).
Sodium Regulation
Sodium ions make up approximately 90% of extracellular cations, with a normal blood plasma concentration of 136–148 mEq/L. A decrease in blood volume and pressure triggers the release of renin from granular cells in the juxtaglomerular complex (JGC), primarily in...
The Role of Ion Channels in Neuronal Computation01:19

The Role of Ion Channels in Neuronal Computation

A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
Non-gated Ion Channels01:24

Non-gated Ion Channels

Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.

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Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes
10:19

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes

Published on: January 10, 2011

Kir4.1 K+ channels are regulated by external cations.

Johan M Edvinsson1, Anish J Shah, Lawrence G Palmer

  • 1Graduate Program in Physiology, Biophysics and Systems Biology, Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY, USA.

Channels (Austin, Tex.)
|May 3, 2011
PubMed
Summary

Inwardly rectifying potassium channel (Kir) 4.1 is regulated by extracellular potassium. Changes in extracellular potassium concentration alter Kir4.1 currents, indicating a sensing mechanism within the channel.

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Last Updated: Jun 2, 2026

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes
10:19

Patch Clamp and Perfusion Techniques for Studying Ion Channels Expressed in Xenopus oocytes

Published on: January 10, 2011

Recapitulation of an Ion Channel IV Curve Using Frequency Components
10:14

Recapitulation of an Ion Channel IV Curve Using Frequency Components

Published on: February 8, 2011

Double-barreled and Concentric Microelectrodes for Measurement of Extracellular Ion Signals in Brain Tissue
11:08

Double-barreled and Concentric Microelectrodes for Measurement of Extracellular Ion Signals in Brain Tissue

Published on: September 5, 2015

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Biophysics

Background:

  • The inwardly rectifying potassium channel (Kir) 4.1 plays a crucial role in spatial potassium buffering within the central nervous system (CNS).
  • Kir4.1 function is potentially influenced by a wide spectrum of extracellular potassium concentrations ([K(+)]o).

Purpose of the Study:

  • To investigate the regulation of Kir4.1 by extracellular potassium concentrations.
  • To elucidate the mechanism by which Kir4.1 senses and responds to changes in its ionic environment.

Main Methods:

  • Whole-cell patch-clamp electrophysiology in Xenopus oocytes expressing Kir4.1.
  • Investigated the effects of varying [K(+)]o on Kir4.1 currents.
  • Utilized voltage-dependent blockers (Cs+, Ba2+) and permeant ions (Rb+, NH4+) to probe channel regulation.
  • Developed a kinetic model of ion permeation.

Main Results:

  • Kir4.1 currents exhibit slow (minute timescale) increases with elevated [K(+)]o and decreases upon K+ removal.
  • This regulation is independent of the channel's pHi-sensitive gate and the K67 residue.
  • Cs+ and Ba2+ can substitute for K+ in preventing deactivation in low [K(+)]o, with Cs+ binding and regulating the channel similarly.
  • While both Rb+ and NH4+ permeate Kir4.1, only Rb+ effectively regulates the channel.
  • A kinetic model supports the hypothesis that Kir4.1 senses the extracellular ionic environment via selectivity filter ion occupancy patterns.

Conclusions:

  • Kir4.1 is regulated by ions interacting with specific sites within its selectivity filter.
  • The channel can distinguish between ions with similar permeation properties (e.g., Rb+ and NH4+), allowing it to sense extracellular ionic conditions without necessarily blocking permeation.