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Membrane potential

About: Membrane potential is a research topic. Over the lifetime, 18754 publications have been published within this topic receiving 939624 citations. The topic is also known as: transmembrane potential & membrane voltage.


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Journal ArticleDOI
02 Feb 1984-Nature
TL;DR: The voltage dependence of the NMDA receptor-linked conductance appears to be a consequence of the voltage dependenceof the Mg2+ block and its interpretation does not require the implication of an intramembrane voltage-dependent ‘gate’.
Abstract: The responses of vertebrate neurones to glutamate involve at least three receptor types. One of these, the NMDA receptor (so called because of its specific activation by N-methyl-D-aspartate), induces responses presenting a peculiar voltage sensitivity. Above resting potential, the current induced by a given dose of glutamate (or NMDA) increases when the cell is depolarized. This is contrary to what is observed at classical excitatory synapses, and recalls the properties of 'regenerative' systems like the Na+ conductance of the action potential. Indeed, recent studies of L-glutamate, L-aspartate and NMDA-induced currents have indicated that the current-voltage (I-V) relationship can show a region of 'negative conductance' and that the application of these agonists can lead to a regenerative depolarization. Furthermore, the NMDA response is greatly potentiated by reducing the extracellular Mg2+ concentration [( Mg2+]o) below the physiological level (approximately 1 mM). By analysing the responses of mouse central neurones to glutamate using the patch-clamp technique, we have now found a link between voltage sensitivity and Mg2+ sensitivity. In Mg2+-free solutions, L-glutamate, L-aspartate and NMDA open cation channels, the properties of which are voltage independent. In the presence of Mg2+, the single-channel currents measured at resting potential are chopped in bursts and the probability of opening of the channels is reduced. Both effects increase steeply with hyperpolarization, thereby accounting for the negative slope of the I-V relationship of the glutamate response. Thus, the voltage dependence of the NMDA receptor-linked conductance appears to be a consequence of the voltage dependence of the Mg2+ block and its interpretation does not require the implication of an intramembrane voltage-dependent 'gate'.

3,977 citations

Book ChapterDOI
01 Jan 1996
TL;DR: The action potential is triggered when the membrane potential, which was at the resting level, depolarizes and reaches the threshold of excitation, which triggers the action potential.
Abstract: Excitability. Excitability of cell membranes is crucial for signaling in many types of cell. Excitation in the physiological sense means that the cell membrane potential undergoes characteristic changes which, in most cases, go in the depolarizing direction. Single depolarization from the resting potential to potentials near 0 mV has generally been called an action potential. A schematic representation of a neuronal action potential is given in Fig. 12.1 A. The action potential is triggered when the membrane potential, which was at the resting level, depolarizes and reaches the threshold of excitation. This depolarization, which triggers the action potential, is generated by depolarizing synaptic currents, or depolarizing current coming from a membrane region that is already excited (propagation of an action potential), or by pacemaker currents mediated by pacemaker channels, or by current injected externally by an electrode. The duration of different types of action potential varies from seconds to less than 1 ms.

3,016 citations

Journal ArticleDOI
17 May 1984-Nature
TL;DR: Using voltage-clamp experiments on mouse spinal cord neurones, it is shown that the voltage-sensitivity of NMDA action is greatly reduced on the withdrawal of physiological concentrations (∼1 mM) of Mg2+ from the extracellular fluid, providing further evidence that Mg 2+ blocks inward current flow through ion channels linked to NMDA receptors.
Abstract: Acidic amino acids are putative excitatory synaptic transmitters1,2, the ionic mechanism of which is not well understood. Recent studies with selective agonists and antagonists suggest that neurones of the mammalian central nervous system possess several different receptors for acidic amino acids3,4, which in turn are coupled to separate conductance mechanisms5. N-methyl-D-aspartic acid (NMDA) is a selective agonist for one of these receptors3,4. The excitatory action of amino acids acting at NMDA receptors is remarkably sensitive to the membrane potential and it has been suggested that the NMDA receptor is coupled to a voltage-sensitive conductance6–9. Recently, patch-clamp experiments have shown the voltage-dependent block by Mg2+ of current flow through ion channels activated by L-glutamate10. We now show using voltage-clamp experiments on mouse spinal cord neurones that the voltage-sensitivity of NMDA action is greatly reduced on the withdrawal of physiological concentrations (∼1 mM) of Mg2+ from the extracellular fluid. This provides further evidence that Mg2+ blocks inward current flow through ion channels linked to NMDA receptors.

2,810 citations

Journal ArticleDOI
TL;DR: It is demonstrated by functional expression, both in oocytes of Xenopus laevis and mammalian cells, that ChR2 is a directly light-switched cation-selective ion channel, and may be used to depolarize small or large cells, simply by illumination.
Abstract: Microbial-type rhodopsins are found in archaea, prokaryotes, and eukaryotes. Some of them represent membrane ion transport proteins such as bacteriorhodopsin, a light-driven proton pump, or channelrhodopsin-1 (ChR1), a recently identified light-gated proton channel from the green alga Chlamydomonas reinhardtii. ChR1 and ChR2, a related microbial-type rhodopsin from C. reinhardtii, were shown to be involved in generation of photocurrents of this green alga. We demonstrate by functional expression, both in oocytes of Xenopus laevis and mammalian cells, that ChR2 is a directly light-switched cation-selective ion channel. This channel opens rapidly after absorption of a photon to generate a large permeability for monovalent and divalent cations. ChR2 desensitizes in continuous light to a smaller steady-state conductance. Recovery from desensitization is accelerated by extracellular H+ and negative membrane potential, whereas closing of the ChR2 ion channel is decelerated by intracellular H+. ChR2 is expressed mainly in C. reinhardtii under low-light conditions, suggesting involvement in photoreception in dark-adapted cells. The predicted seven-transmembrane α helices of ChR2 are characteristic for G protein-coupled receptors but reflect a different motif for a cation-selective ion channel. Finally, we demonstrate that ChR2 may be used to depolarize small or large cells, simply by illumination.

2,519 citations

Book ChapterDOI
30 May 2008
TL;DR: Comparisons can now be made between the kinetics of the ionic conductances as described by Hodgkin & Huxley, and the steady-state distribution and kinetic changes of the charged controlling particles, which should lead to useful conclusions about the intramolecular organization of the sodium channels and the conformational changes that take place under the influence of the electric field.
Abstract: The ionic channels in excitable membranes are of two classes: those that open and close when the membrane potential alters and those that respond to the release of an appropriate chemical transmitter. The former are responsible for the conduction of impulses in nerve and muscle fibres and the latter for synaptic transmission. It is now clear that the sodium and potassium channels in electrically excitable membranes are functionally distinct, since each can be blocked without affecting the behaviour of the other. It has recently proved possible to study, in the voltage-clamped squid giant axon, the movements of the mobile charges or dipoles that form the voltage-sensitive portion of the sodium channels, which give rise to the so-called 'gating' current. Detailed comparisons can now be made between the kinetics of the ionic conductances as described by Hodgkin & Huxley, and the steady-state distribution and kinetics of the charged controlling particles, which should lead to useful conclusions about the intramolecular organization of the sodium channels and the conformational changes that take place under the influence of the electric field. There is as yet little information about the chemical nature of the electrically excitable channels, but significant progress has been made towards the isolation and characterization of the acetylcholine receptors in muscle and electric organ.

2,489 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023152
2022231
2021217
2020239
2019236
2018249