scholarly journals K Permeability of Nitella clavata in the Depolarized State

1973 ◽  
Vol 62 (5) ◽  
pp. 535-549 ◽  
Author(s):  
Hiroshi Kitasato
Keyword(s):  
Membrane Potential ◽  
Finite Number ◽  
Potassium Conductance ◽  
Membrane Potentials ◽  
Membrane Current ◽  
Half Maximum ◽  
Membrane Potential Change ◽  
Potassium Permeability ◽  
Maximum Value ◽  
K Permeability

Membrane current responses to sudden potential changes were recorded in solutions of various [K]o on 52 internodal cells of Nitella clavata. The membrane current after sudden depolarization had a component sensitive to [K]o which increased with time from 0.3 to 2.0 s and remained steady thereafter. This late current became zero at values of E and [K]o which suggests that the current was nearly all carried by K+. The potassium conductivity represented by this current increased with depolarization, with a half-maximum value at about -70 mV, and saturation at about -30 to -20 mV. The potassium conductance also increased with increasing [K]o, but less rapidly than predicted for constant potassium permeability. This failure of the conductance to increase with [K]o was relatively the same at all membrane potentials and may be explained by a model with a finite number of channels. No attempt was made to model the dependence of gK on time after depolarization or on membrane potential. However, the finding that the membrane potential did not affect the way in which the permeability depended on [K]o suggests that the membrane potential change does not affect the affinity of the sites, and that the increase in gK with time after depolarization is brought about by an increase in the number of channels with such sites.

scholarly journals Multiple Serotonin-Activated Currents in Isolated, Neuronal Somata from Locust Thoracic Ganglia

1992 ◽  
Vol 165 (1) ◽  
pp. 43-60 ◽  
Author(s):  
ISABEL BERMUDEZ ◽  
DAVID J. BEADLE ◽  
JACK A. BENSON
Keyword(s):  
Membrane Potential ◽  
Potassium Conductance ◽  
Membrane Conductance ◽  
Membrane Potentials ◽  
Potential Range ◽  
Neuronal Somata ◽  
Sodium Permeability ◽  
Fast Kinetics ◽  
Thoracic Ganglia ◽  
Slow Kinetics

1. Three different responses were evoked by pressure micro-application of serotonin onto freshly dissociated, current- and voltage-clamped neuronal somata from the thoracic ganglia of the locust Locusta migratoria. 2. In some neurones, an inward current, I(5HT)K, resulting from a decrease in potassium conductance, with slow kinetics and maximum activation at membrane potentials of −60 to - 70 mV, was evoked by serotonin and by the 5-HT3 agonist 2-methyl serotonin. This current was completely abolished by either 10 mmoll−1 caesium or 5 mmoll−1 rubidium and partially blocked by 50 mmoll−1 tetraethylammonium or 5 mmoll−1 4-aminopyridine. The response was antagonised by the 5-HT2-specific compounds, ketanserin and ritanserin. 3. In other somata, serotonin, 2-methyl serotonin and the 5-HT3 antagonist ICS205 930 evoked a second current, I(5HT)Na, which was due to an increase in sodium permeability and had slow kinetics similar to that of I(5HT)K. This current was inward over the membrane potential range −30 to - 80 mV and increased with hyperpolarisation. The response was blocked by sodium-free saline and the 5-HT3 receptor antagonist MDL 72222. 4. In other neurones, at membrane potentials more positive than - 50 mV, serotonin pulses could activate a third current, I(5HT)X, which increased with depolarisation of the membrane potential and had comparatively fast kinetics. Activation of the current was accompanied by a decrease in membrane conductance. This response was completely blocked by 4-aminopyridine and weakly inhibited by both caesium and tetraethylammonium and is, therefore, probably a potassium current. 5. The three currents described here differ in their pharmacology, their ionic mechanisms and their dependence on membrane potential from the serotoninactivated currents reported for vertebrates and they provide evidence for the mechanism of action of serotonin as a neurotransmitter in insects. Note: Present address: Pharmacology Institute, University of Zurich, Gloriastrasse 32, CH-8006 Zurich, Switzerland.

scholarly journals On the Wireless Microwave Sensing of Bacterial Membrane Potential in Microfluidic-Actuated Platforms

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3420
Author(s):  
Marc Jofre ◽  
Lluís Jofre ◽  
Luis Jofre-Roca
Keyword(s):  
Membrane Potential ◽  
Living Cells ◽  
Membrane Potentials ◽  
Electromagnetic Properties ◽  
Bacterial Membrane ◽  
Microfluidic Platforms ◽  
Bacterial Membranes ◽  
Wireless Monitoring ◽  
Bacterial Dynamics ◽  
Engineered Systems

The investigation of the electromagnetic properties of biological particles in microfluidic platforms may enable microwave wireless monitoring and interaction with the functional activity of microorganisms. Of high relevance are the action and membrane potentials as they are some of the most important parameters of living cells. In particular, the complex mechanisms of a cell’s action potential are comparable to the dynamics of bacterial membranes, and consequently focusing on the latter provides a simplified framework for advancing the current techniques and knowledge of general bacterial dynamics. In this work, we provide a theoretical analysis and experimental results on the microwave detection of microorganisms within a microfluidic-based platform for sensing the membrane potential of bacteria. The results further advance the state of microwave bacteria sensing and microfluidic control and their implications for measuring and interacting with cells and their membrane potentials, which is of great importance for developing new biotechnologically engineered systems and solutions.

scholarly journals Evoked membrane potential change in rat optic nerve fiber: Computer simulation

2007 ◽  
Vol 23 (6) ◽  
pp. 348-356 ◽  
Author(s):  
Vincent Cazenave-Loustalet ◽  
Qing-Li Qiao ◽  
Li-Ming Li ◽  
Qiu-Shi Ren
Keyword(s):  
Computer Simulation ◽  
Membrane Potential ◽  
Optic Nerve ◽  
Nerve Fiber ◽  
Potential Change ◽  
Membrane Potential Change ◽  
Optic Nerve Fiber

Modulation of membrane potential by an acetylcholine-activated potassium current in trout atrial myocytes

2007 ◽  
Vol 292 (1) ◽  
pp. R388-R395 ◽  
Author(s):  
Cristina E. Molina ◽  
Hans Gesser ◽  
Anna Llach ◽  
Lluis Tort ◽  
Leif Hove-Madsen
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Ventricular Myocytes ◽  
Reversal Potential ◽  
Membrane Potentials ◽  
Resting Membrane Potential ◽  
Atrial Myocytes ◽  
Atrial Tissue ◽  
Isolated Cardiac Myocytes ◽  
Inwardly Rectifying

Application of the current-clamp technique in rainbow trout atrial myocytes has yielded resting membrane potentials that are incompatible with normal atrial function. To investigate this paradox, we recorded the whole membrane current ( Im) and compared membrane potentials recorded in isolated cardiac myocytes and multicellular preparations. Atrial tissue and ventricular myocytes had stable resting potentials of −87 ± 2 mV and −83.9 ± 0.4 mV, respectively. In contrast, 50 out of 59 atrial myocytes had unstable depolarized membrane potentials that were sensitive to the holding current. We hypothesized that this is at least partly due to a small slope conductance of Im around the resting membrane potential in atrial myocytes. In accordance with this hypothesis, the slope conductance of Im was about sevenfold smaller in atrial than in ventricular myocytes. Interestingly, ACh increased Im at −120 mV from 4.3 pA/pF to 27 pA/pF with an EC50 of 45 nM in atrial myocytes. Moreover, 3 nM ACh increased the slope conductance of Im fourfold, shifted its reversal potential from −78 ± 3 to −84 ± 3 mV, and stabilized the resting membrane potential at −92 ± 4 mV. ACh also shortened the action potential in both atrial myocytes and tissue, and this effect was antagonized by atropine. When applied alone, atropine prolonged the action potential in atrial tissue but had no effect on membrane potential, action potential, or Im in isolated atrial myocytes. This suggests that ACh-mediated activation of an inwardly rectifying K+ current can modulate the membrane potential in the trout atrial myocytes and stabilize the resting membrane potential.

scholarly journals Method of Determining Seed Germination by Using Membrane Potential of Wheat Seeds

2019 ◽  
Vol 29 (3) ◽  
pp. 443-455 ◽  
Author(s):  
Nadezhda N. Barysheva ◽  
Sergey P. Pronin
Keyword(s):  
Membrane Potential ◽  
Rapid Assessment ◽  
Membrane Potentials ◽  
Seeding Rate ◽  
Important Indicator ◽  
Agricultural Enterprises ◽  
Highly Sensitive ◽  
Technological Stage ◽  
Seeds Germination ◽  
Wheat Seeds

Introduction. The germination of wheat seeds is an important indicator of their quality, used to calculate and adjust the seeding rate. It is necessary to take into account germination changes at the storage stage. The solution of this problem will be development of a method that will allow to determinate germination at any technological stage (at the stage of harvesting, storage, seeding).The aim of the article is to study the dependence of membrane potential on grain quality, to develop a method for determining the germination of wheat seeds based on their membrane potentials. Materials and Methods. The authors' review of research papers about methods of assessing the wheat seeds quality indicates the need for the development of highly sensitive methods of the germination test, which allow one to ensure the speed of measurement and obtain more accurate results for further use. An approach was developed on the basis of the review, which allows for solving the problem using the method based on the study of membrane potentials of wheat seeds. Results. In this article, the study of the dependence of wheat seeds membrane potential from their germination was conducted. The results of experiments confirmed that the value of the potential could be used as quality assessment parameter. The requirements and optimal conditions for conducting the experiment were determined. Discussion and Conclusion. The dependence of the wheat seeds membrane potential on their germination was established and the method for determining wheat seeds germination was developed. The implementation of this method will allow agricultural enterprises and farms to carry out the rapid assessment of wheat seeds germination at any technological stage (at the stage of harvesting, storage, seeding).

Membrane Potentials in Amoeba Proteus

1966 ◽  
Vol 45 (2) ◽  
pp. 251-267
Author(s):  
M. S. BINGLEY
Keyword(s):  
Plasma Membrane ◽  
Membrane Potential ◽  
Morphological Changes ◽  
Amoeba Proteus ◽  
Membrane Potentials ◽  
The Other ◽  
The Earth ◽  
Electrode Resistance ◽  
Alternating Voltage

1. Amoebae can be penetrated by microelectrodes at either end. One records voltage and the other supplies alternating current. 2. Step-like increases in alternating voltage superimposed on potentials recorded by the voltage electrode when in either the pseudopod or rear region demonstrate that low potentials recorded from a pseudopod and high ones from the rear region exist across a discrete impedance barrier. The only structure so far shown to fulfil this function is the plasma membrane. 3. A resistance inserted in the earth path monitors current flowing through the system and confirms observations made when recording with single electrodes that there is a reduction of electrode resistance when the cell is entered. 4. Pronounced depolarization in the rear region is shown when the current-carrying electrode penetrates the pseudopod, but not vice versa. 5. Morphological changes associated with membrane potential reversal are illustrated. 6. Consideration is given to the role of step-like potential changes in movement.

Conductance changes underlying a late synaptic hyperpolarization in hippocampal CA3 neurons

1987 ◽  
Vol 58 (1) ◽  
pp. 160-179 ◽  
Author(s):  
J. J. Hablitz ◽  
R. H. Thalmann
Keyword(s):  
Membrane Potential ◽  
Voltage Clamp ◽  
Time Course ◽  
Membrane Potentials ◽  
Resting Membrane Potential ◽  
Extracellular Potassium ◽  
Voltage Sensitivity ◽  
Base Line ◽  
Membrane Hyperpolarization ◽  
Ca3 Neurons

1. Single-electrode current- and voltage-clamp techniques were employed to study properties of the conductance underlying an orthodromically evoked late synaptic hyperpolarization or late inhibitory postsynaptic potential (IPSP) in CA3 pyramidal neurons in the rat hippocampal slice preparation. 2. Late IPSPs could occur without preceding excitatory postsynaptic potentials at the resting membrane potential and were graded according to the strength of the orthodromic stimulus. The membrane hyperpolarization associated with the late IPSP peaked within 140-200 ms after orthodromic stimulation of mossy fiber afferents. The late IPSP returned to base line with a half-decay time of approximately 200 ms. 3. As determined from constant-amplitude hyperpolarizing-current pulses, the membrane conductance increase during the late IPSP, and the time course of its decay, were similar whether measurements were made near the resting membrane potential or when the cell was hyperpolarized by approximately 35 mV. 4. When 1 mM cesium was added to the extracellular medium to reduce inward rectification, late IPSPs could be examined over a range of membrane potentials from -60 to -140 mV. For any given neuron, the late IPSP amplitude-membrane potential relationship was linear over the same range of membrane potentials for which the slope input resistance was constant. The late IPSP reversed symmetrically near -95 mV. 5. Intracellular injection of ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid or extracellular application of forskolin, procedures known to reduce or block certain calcium-dependent potassium conductances in CA3 neurons, had no significant effect on the late IPSP. 6. Single-electrode voltage-clamp techniques were used to analyze the time course and voltage sensitivity of the current underlying the late IPSP. This current [the late inhibitory postsynaptic current (IPSC)] began as early as 25 ms after orthodromic stimulation and reached a peak 120-150 ms following stimulation. 7. The late IPSC decayed with a single exponential time course (tau = 185 ms). 8. A clear reversal of the late IPSC at approximately -99 mV was observed in a physiological concentration of extracellular potassium (3.5 mM).(ABSTRACT TRUNCATED AT 400 WORDS)

Synaptic and intrinsic control of membrane excitability of neostriatal neurons. II. An in vitro analysis

1990 ◽  
Vol 63 (4) ◽  
pp. 663-675 ◽  
Author(s):  
P. Calabresi ◽  
N. B. Mercuri ◽  
G. Bernardi
Keyword(s):  
Membrane Potential ◽  
Tetanus Toxin ◽  
Reversal Potential ◽  
Membrane Potentials ◽  
Synaptic Activity ◽  
Membrane Properties ◽  
Membrane Excitability ◽  
Epsp Amplitude ◽  
The Relationship

1. The effects of intrinsic membrane properties on the spontaneous and synaptically evoked activity of neostriatal neurons were studied in an in vitro slice preparation with the use of intracellular recordings. The recorded neurons did not show spontaneous action potentials at rest; depolarizing current pulses triggered a tonic firing pattern. 2. Subthreshold spontaneous depolarizing potentials (SDPs) were observed in 52% of the recorded neurons. The amplitude of these potentials at rest ranged between 2 and 15 mV, and their duration between 4 and 100 ms. The frequency and the amplitude of the SDPs were functions of the membrane potential: membrane depolarization by constant positive current increased the frequency of the SDPs and reduced their amplitude; hyperpolarization of the membrane decreased their frequency and increased their amplitude. Often, at membrane potentials more negative than -90 mV, SDPs were completely suppressed. 3. SDPs were blocked by low calcium-cobalt containing solutions. In the presence of tetrodotoxin (TTX, 1-3 microM), SDPs were completely abolished in 50% of the tested neurons; in the remaining neurons, small (1-4 mV) TTX-resistant SDPs were observed. In most of the neurons, bicuculline (BIC, 10-100 microM) and low concentrations of tetanus toxin (5-10 micrograms/ml) did not clearly affect the SDPs. Higher concentrations of tetanus toxin (100 micrograms/ml) blocked the SDPs as well as the synaptic potentials evoked by intrastriatal stimulation. 4. At resting membrane potential, intrastriatal stimulation produced a fast depolarizing postsynaptic potential (EPSP) that was reduced by BIC (10-100 microM). The relationship between EPSP amplitude and membrane potential was studied either by utilizing K(+)-chloride electrodes or by the use of cesium-chloride electrodes. In both these cases, the reversal potential for the EPSPs was between 0 and -14 mV. In cesium-loaded neurons, the decrease of the EPSP, usually observed at negative membrane potentials (below -85 mV), was clearly reduced. Internal cesium prolonged the duration of the SDPs and the EPSPs evoked by intrastriatal stimulation. 5. The relationship between spontaneous and evoked synaptic activity and membrane potential was studied in the presence of different external potassium blockers. 4-Aminopyridine (4AP, 0.1-1 mM) increased the EPSP amplitude and the frequency of the SDPs, but did not decrease membrane rectification and the shunt of the EPSPs present at negative membrane potentials. On the contrary, rectification of the membrane and the shunt of the EPSPs below -85 mV were clearly reduced by tetraethylammonium (TEA, 10-20 mM).(ABSTRACT TRUNCATED AT 400 WORDS)

Barium inhibition of basolateral membrane potassium conductance in tracheal epithelium

1983 ◽  
Vol 244 (6) ◽  
pp. F639-F645 ◽  
Author(s):  
M. J. Welsh
Keyword(s):  
Driving Force ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Potassium Conductance ◽  
Short Circuit Current ◽  
Electrical Circuit ◽  
Tracheal Epithelium ◽  
Bathing Solution ◽  
K Permeability

Addition of barium ion, Ba2+, to the submucosal bathing solution of canine tracheal epithelium reversibly decreased the short-circuit current and increased transepithelial resistance. The decrease in short-circuit current represented a decrease in the net rate of Cl secretion with no change in the rate of Na absorption. Intracellular microelectrode techniques and an equivalent electrical circuit analysis were used to localize the effect of Ba2+ to an inhibition of the permeability of the basolateral membrane to K. Ba2+ (2 mM) doubled basolateral membrane resistance, decreased the equivalent electromotive force at the basolateral membrane, and decreased the magnitude of the depolarization of basolateral membrane voltage produced by increasing the submucosal K concentration. The inhibition of the basolateral K permeability depolarized the negative intracellular voltage, resulting in both a decrease in the driving force for Cl exit and an estimated increase in intracellular Cl concentration. These studies indicate that there is a Ba2+-inhibitable K conductance at the basolateral membrane of tracheal epithelial cells and that the K permeability plays an important role in the generation of the negative intracellular electrical potential that provides the driving force for Cl exit from the cell.

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