Negative shift of cardiac Na+ channel kinetics in cell-attached patch recordings

1990 ◽  
Vol 258 (1) ◽  
pp. H247-H254 ◽  
Author(s):  
T. Kimitsuki ◽  
T. Mitsuiye ◽  
A. Noma
Keyword(s):  
Patch Clamp ◽  
Single Channel ◽  
Resting Potential ◽  
Na Channel ◽  
Channel Kinetics ◽  
Patch Clamp Technique ◽  
Inactivation Curve ◽  
Pipette Solution ◽  
Single Channel Currents ◽  
Channel Currents

Na+ channel kinetics were studied by recording single-channel currents in the cell-attached patch configuration of the patch-clamp technique in single ventricular cells isolated from guinea pig hearts. The inactivation time course of ensemble currents was accelerated, and the peak amplitude increased temporarily and then decreased within a few minutes after the gigaohm seal formation. After reaching a new steady state, the inactivation-voltage relation was found to have shifted to more negative potentials. The potential of half-maximal inactivation was more negative by 20–31 mV from the resting potential or between -96 and -112 mV. The voltage dependency of the channel activation also shifted. Although the cell membrane was depolarized using the whole cell patch-clamp electrode and single-channel currents were recorded with an independent cell-attached electrode, the shift of the inactivation curve was also evident. Complete removal of Ca2+ using 5 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid in the pipette solution failed to prevent the shift. Increasing Ca2+ to 10 mM, however, reduced magnitude of the shift significantly. Involvement of an increased membrane fluidity and surface potential of the glass pipette to the shift is discussed.

Nonselective cation and Cl channels in luminal membrane of the marginal cell

1993 ◽  
Vol 265 (1) ◽  
pp. C72-C78 ◽  
Author(s):  
H. Sunose ◽  
K. Ikeda ◽  
Y. Saito ◽  
A. Nishiyama ◽  
T. Takasaka
Keyword(s):  
Single Channel ◽  
Patch Clamp Technique ◽  
Cl Channel ◽  
Luminal Membrane ◽  
Cl Channels ◽  
Cytoplasmic Acidification ◽  
Marginal Cells ◽  
Single Channel Currents ◽  
Channel Currents ◽  
Linear Conductance

Single-channel currents of the luminal membrane of marginal cells dissected from the guinea pig cochlea were investigated using the patch-clamp technique. Nonselective cation channels having a linear conductance of 27 pS were activated by depolarization, cytoplasmic Ca2+, and cytoplasmic acidification. Cytoplasmic ATP inactivated the channel. A mixture of 3-isobutyl-1-methylxanthine and forskolin activated a small-conductance Cl channel in the cell-attached mode. On excision in the inside-out mode, the Cl channel was inactivated, but it was reactivated by a cytoplasmic catalytic subunit of protein kinase A with ATP. This Cl channel had a linear conductance of 12 pS, and its activity was little affected by voltage. The sequence of permeation by anions was Br- > Cl > I-. The Cl channel blocker diphenylamine-2-carboxylic acid (3 mM) completely blocked the channel, but 5-nitro-2-(3-phenylpropylamino)-benzoic acid (50 microM) blocked it only partially. The above-mentioned characteristics are similar to those of the well-demonstrated Cl- channel, cystic fibrosis transmembrane regulator.

Chloride channels in cultured glomus cells of the rat carotid body

1989 ◽  
Vol 257 (2) ◽  
pp. C174-C181 ◽  
Author(s):  
A. Stea ◽  
C. A. Nurse
Keyword(s):  
Carotid Body ◽  
Chloride Channels ◽  
Single Channel ◽  
Resting Potential ◽  
Chloride Permeability ◽  
Patch Clamp Technique ◽  
Glomus Cells ◽  
Ion Substitution ◽  
Stilbene Derivatives ◽  
Single Channel Currents

As part of our investigations on the chemosensory mechanisms in the rat carotid body, we are studying the physiology of the parenchymal glomus cells by the patch-clamp technique. Here we characterize a large-conductance chloride channel (approximately 296 pS) with random open and closed kinetics in inside-out patches of cultured glomus cells. The open-state probability (Po; mean = 0.61) was hardly affected by membrane potential (-50 to +50 mV) and cytoplasmic calcium (0-1 mM). Similarly, the channel did not appear to be regulated by cytoplasmic nucleotides (1 mM) or pH (6.5-8). Ion-substitution experiments yielded the following selectivity sequence: chloride greater than bicarbonate greater than sulfate greater than glutamate approximately sodium. Single-channel currents were reversibly reduced or blocked by anthracene-9-carboxylic acid (5-10 mM) but were unaffected by stilbene derivatives (0.5-1 mM), by furosemide (1 mM), and by 5-nitro-2-(3-phenyl-propylamino)benzoic acid (0.01 mM). Because these cultured glomus cells have been shown to express carbonic anhydrase, it is inferred that the chloride channels may play an important role in the physiology of glomus cells by aiding in the regulation of pHi and the resting potential via bicarbonate and chloride permeability.

Spontaneous and GABA-induced single channel currents in cultured murine spinal cord neurons

1985 ◽  
Vol 63 (10) ◽  
pp. 1228-1233 ◽  
Author(s):  
David A. Mathers
Keyword(s):  
Spinal Cord ◽  
Time Constant ◽  
Single Channel ◽  
Resting Potential ◽  
Embryonic Mouse ◽  
Spinal Cord Neurons ◽  
Frequency Distributions ◽  
Exponential Term ◽  
Single Channel Currents ◽  
Channel Currents

Intracellular and patch clamp recordings were made from embryonic mouse spinal cord neurons growing in primary cell culture. Outside-out membrane patches obtained from these cells usually showed spontaneous single channel currents when studied at the resting potential (−56 ± 1.5 mV). In 18 out of 30 patches tested, spontaneous single channel activity was abolished by making Tris+ the major cation on both sides of the membrane. The remaining patches continued to display spontaneous single channel currents under these conditions. These events reversed polarity at a patch potential of 0 mV and displayed a mean single channel conductance of 24 ± 1.2 pS. Application of the putative inhibitory transmitter γ-aminobutyric acid (0.5–10 μM) to outside-out patches of spinal cord cell membrane induced single channel currents in 10 out of 15 patches tested. These channels had a primary conductance of 29 ± 2.8 pS in symmetrical 145 mM Cl solutions. Frequency distributions for the open times of these channels were well fit by the sum of a fast exponential term ("of") with a time constant τof = 4 ± 1.3 ms and a slow exponential term ("os") with a time constant τos = 24 ± 8.1 ms. Frequency distributions for channel closed times were also well fit by a double exponential equation, with time constants τcf = 2 ± 0.2 ms and τcs = 62 ± 20.9 ms.

Potassium Channels and Fluid Secretion

Physiology ◽  
1986 ◽  
Vol 1 (3) ◽  
pp. 92-95
Author(s):  
OH Peterson
Keyword(s):  
Potassium Channels ◽  
Patch Clamp ◽  
Single Channel ◽  
Acinar Cells ◽  
Fluid Secretion ◽  
Exocrine Glands ◽  
Great Precision ◽  
K Channels ◽  
Single Channel Currents ◽  
Channel Currents

Fluid secretion from exocrine glands can be switched on and off with great precision. Recent patch-clamp recordings of single-channel currents in acinar cells reveals that neurotransmitters and hormones control the opening of K+ channels. However, fluid secretion is due to transport of Na+ and Cl-, and movement of these ions occurs only when K+ can be transported simultaneously. Thus, by controlling K+ channels, neurotransmitters or hormones regulate Na+ and Cl-secretion.

scholarly journals Nitric oxide augments single persistent Na+ channel currents via the cGMP/PKG signaling pathway in Kenyon cells isolated from cricket mushroom bodies

2018 ◽  
Vol 120 (2) ◽  
pp. 720-728 ◽  
Author(s):  
Mariko Ikeda ◽  
Masami Yoshino
Keyword(s):  
Nitric Oxide ◽  
Signaling Pathway ◽  
Single Channel ◽  
Signaling Cascade ◽  
Mushroom Bodies ◽  
Na Channel ◽  
No Production ◽  
Kenyon Cells ◽  
Single Channel Currents ◽  
Channel Currents

The nitric oxide (NO)/cyclic GMP signaling pathway has been suggested to be important in the formation of olfactory memory in insects. However, the molecular targets of the NO signaling cascade in the central neurons associated with olfactory learning and memory have not been fully analyzed. In this study, we investigated the effects of NO donors on single voltage-dependent Na+ channels in intrinsic neurons, called Kenyon cells, in the mushroom bodies in the brain of the cricket. Step depolarization on cell-attached patch membranes induces single-channel currents with fast-activating and -inactivating brief openings at the beginning of the voltage steps followed by more persistently recurring brief openings all along the 150-ms pulses. Application of the NO donor S-nitrosoglutathione (GSNO) increased the number of channel openings of both types of single Na+ channels. This excitatory effect of GSNO on the activity of these Na+ channels was diminished by KT5823, an inhibitor of protein kinase G (PKG), indicating an involvement of PKG in the downstream pathway of NO. Application of KT5823 alone decreased the activity of the persistent Na+ channels without significant effects on the fast-inactivating Na+ channels. The membrane-permeable cGMP analog 8Br-cGMP increased the number of channel openings of both types of single Na+ channels, similar to the action of NO. Taken together, these results indicate that NO acts as a critical modulator of both fast-inactivating and persistent Na+ channels and that persistent Na+ channels are constantly upregulated by the endogenous cGMP/PKG signaling cascade. NEW & NOTEWORTHY This study clarified that nitric oxide (NO) increases the activity of both fast-inactivating and persistent Na+ channels via the cGMP/PKG signaling cascade in cricket Kenyon cells. The persistent Na+ channels are also found to be upregulated constantly by endogenous cGMP/PKG signaling. On the basis of the present results and the results of previous studies, we propose a hypothetical model explaining NO production and NO-dependent memory formation in cricket large Kenyon cells.

Regulation of low-amiloride-affinity sodium channels in alveolar type II cells

1994 ◽  
Vol 267 (1) ◽  
pp. L94-L100 ◽  
Author(s):  
G. Yue ◽  
R. L. Shoemaker ◽  
S. Matalon
Keyword(s):  
Single Channel ◽  
Alveolar Type ◽  
Type Ii ◽  
Channel Conductance ◽  
Open Probability ◽  
Pipette Solution ◽  
Ionic Substitution ◽  
Beta Agonists ◽  
Single Channel Currents ◽  
Channel Currents

We determined the mechanisms by which beta-agonists increase sodium (Na+) currents across rat alveolar type II (ATII) cells grown in primary culture. When ATII cells were patched in the cell-attached mode using symmetrical Na+ solutions (150 mM Na(+)-glutamate), single-channel currents were observed for holding potentials between -80 and 30 mV (referenced to the pipette solution) with a single-channel conductance of 27 +/- 3 pS, a mean open time (tau 1) of 3.3 +/- 0.15 ms and an open probability (Po) of 0.36 +/- 0.06 (n = 7). Addition of 10 microM terbutaline into the bath increased tau 1 to 6.43 +/- 0.5 ms and Po to 0.62 +/- 0.06 (n = 7) without affecting channel conductance. Single-channel currents with a conductance of 25 +/- 2 pS were also recorded across ATII cells patched in the inside-out mode. Addition of 250 U/ml of protein kinase A (PKA), 1 mM ATP, and 5 mM MgCl2 in the bath solution (150 mM Na(+)-glutamate) increased the single channel tau 1 from 3.26 +/- 0.15 to 7.38 +/- 0.38 and Po from 0.41 +/- 0.06 to 0.72 +/- 0.07 (n = 6) without altering conductance. Addition of 1 microM amiloride or ethylisopropylamiloride (EIPA) in the pipette solution (150 mM Na(+)-glutamate) blocked single-channel activity almost completely. Ionic substitution experiments showed the relative permeability of Na+ to K+ and Na+ to Cl- to be 7:1 and 8:1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Recording of single γ-aminobutyrate- and acetylcholine-activated receptor channels translated by exogenous mRNA in Xenopus oocytes

1983 ◽  
Vol 218 (1213) ◽  
pp. 481-484 ◽  
Keyword(s):  
High Resolution ◽  
Patch Clamp ◽  
Xenopus Oocytes ◽  
Optic Lobe ◽  
Single Channel ◽  
Patch Clamp Recording ◽  
Chick Optic Lobe ◽  
Single Channel Currents ◽  
Channel Currents

High resolution (‘giga-seal’) patch clamp recording in Xenopus oocytes was used to measure single channel currents from ACh- and GABA-activated receptors. The proteins that make up these receptors had been translated from mRNA derived from, respectively, denervated cat muscle and chick optic lobe.

scholarly journals Kinetic properties of single sodium channels in rat heart and rat brain.

1989 ◽  
Vol 93 (1) ◽  
pp. 85-99 ◽  
Author(s):  
G E Kirsch ◽  
A M Brown
Keyword(s):  
Cortical Neurons ◽  
Single Channel ◽  
Ventricular Myocytes ◽  
Na Channel ◽  
Kinetic Properties ◽  
Open Time ◽  
Excised Patches ◽  
Single Channel Currents ◽  
Channel Currents ◽  
Near Threshold

Single Na channel currents were compared in ventricular myocytes and cortical neurons of neonatal rats using the gigaseal patch-clamp method to determine whether tissue-specific differences in gating can be detected at the single-channel level. Single-channel currents were recorded in cell-attached and excised membrane patches at test potentials of -70 to -20 mV and at 9-11 degrees C. In both cell-attached and excised patches brain Na channel mean open time progressively increased from less than 1 ms at -70 mV to approximately 2 ms at -20 mV. Near threshold, single openings with dispersed latencies were observed. By contrast, in cell-attached patches, heart Na channel mean open time peaked near -50 mV, was three times brain Na channel mean open time, and declined continuously to approximately 2 ms at -20 mV. Near threshold, openings occurred frequently usually as brief bursts lasting several milliseconds and rarely as prolonged bursts lasting tens of milliseconds. Unlike what occurs in brain tissue where excision did not change gating, in excised heart patches both the frequency of prolonged bursting and the mean open time of single units increased markedly. Brain and cardiac Na channels can therefore be distinguished on the basis of their mean open times and bursting characteristics.

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