Effect of adenosine 3',5'-monophosphate on neuronal pacemaker activity: a voltage clamp analysis

Science ◽  
1981 ◽  
Vol 211 (4477) ◽  
pp. 59-61 ◽  
Author(s):  
S. Treistman
Keyword(s):  
Voltage Clamp ◽  
Pacemaker Activity ◽  
Voltage Clamp Analysis

Voltage-clamp analysis of nodes of Ranvier in regenerated rat sciatic nerve

1987 ◽  
Vol 409 (2) ◽  
pp. 227-235 ◽  
Author(s):  
T. Brismar ◽  
C. Hildebrand ◽  
S. Berglund
Keyword(s):  
Sciatic Nerve ◽  
Voltage Clamp ◽  
Nodes Of Ranvier ◽  
Rat Sciatic Nerve ◽  
Voltage Clamp Analysis

Cellular and subcellular mechanisms of cardiac pacemaker oscillations

1979 ◽  
Vol 81 (1) ◽  
pp. 205-215
Author(s):  
R. W. Tsien ◽  
R. S. Kass ◽  
R. Weingart
Keyword(s):  
Membrane Potential ◽  
Voltage Clamp ◽  
Surface Membrane ◽  
Cardiac Pacemaker ◽  
Oscillatory Activity ◽  
Purkinje Fibre ◽  
Pacemaker Activity ◽  
Heart Cells ◽  
Control Loop ◽  
Internal Oscillation

Rhythmic oscillations in the membrane potential of heart cells are important in normal cardiac pacemaker activity as well as cardiac arrhythmias. Two fundamentally different mechanisms of oscillatory activity can be distinguished at the cellular and subcellular level. The first mechanism, referred to as a surface membrane oscillator, can be represented by a control loop in which membrane potential changes evoke delayed conductance changes and vice versa. Since the surface membrane potential is a key variable within the control loop, the oscillation can be interrupted at any time by holding the membrane potential constant with a voltage clamp. This mode of oscillation seems to describe spontaneous pacemaker activity in the primary cardiac pacemaker (sinoatrial node) as well as other regions (Purkinje fibre, atrial or ventricular muscle). In all tissues studied so far, the pacemaker depolarization is dominated by the slow shutting-off of an outward current, largely carried by potassium ions. The second mechanism can be called an internal oscillator since it depends upon a subcellular rhythm generator which is largely independent from the surface membrane. Under voltage clamp, the existence of the internal oscillation is revealed by the presence of oscillations in membrane conductance or contractile force which occur even though the membrane potential is held fixed. The two oscillatory mechanisms are not mutually exclusive; the subcellular mechanism can be preferentially enhanced in any given cardiac cell by conditions which elevate intracellular calcium. Such conditions include digitalis intoxication, high Cao, low Nao, low or high Ko, cooling, or rapid stimulation. Several lines of evidence suggest that the subcellular mechanism involves oscillatory variations in myoplasmic calcium, probably due to cycles of Ca uptake and release by the sarcoplasmic reticulum. The detailed nature of the Cai oscillator and its interaction with the surface membrane await further investigation.

Voltage-clamp analysis of a Ca2+- and voltage-dependent chloride conductance in cultured mouse spinal neurons

1986 ◽  
Vol 55 (6) ◽  
pp. 1115-1135 ◽  
Author(s):  
D. G. Owen ◽  
M. Segal ◽  
J. L. Barker
Keyword(s):  
Voltage Clamp ◽  
Reversal Potential ◽  
Gamma Aminobutyric Acid ◽  
Spinal Neurons ◽  
Exponential Process ◽  
Voltage Clamp Analysis ◽  
Voltage Dependent ◽  
Inward Currents ◽  
Ca 50 ◽  
O 10

Current and voltage-clamp recordings were made at room temperature from cultured mouse spinal neurons using conventional two-electrode voltage-clamp techniques and electrodes filled with either 3 M KCl, 3 M CsCl, or 3 M Cs2SO4. In the presence of tetraethylammonium and tetrodotoxin, “fast” (rapidly rising and falling) action potentials (FAP) of variable duration were recorded in most neurons. “Slow” (slowly rising and falling) depolarizing potentials (SDP) occurred in 23% of the cells, when using KCl-filled electrodes, and in 82% of the cells with CsCl-filled electrodes. The SDP was frequently preceded by an FAP, although in some cells activation of the SDP occurred before the FAP threshold was reached and in a graded fashion. Both the FAP and SDP were abolished by Cd2+ and other Ca2+ antagonists. In cells exhibiting SDPs, voltage-clamp analysis revealed a sustained (noninactivating) inward current (Isin) during depolarizing steps to potentials more positive than -45 mV. Repolarizing steps resulted in slowly decaying inward tail currents (Itail). Both Isin and Itail were abolished in solutions nominally free of Cao2+, or containing Ca2+-channel antagonists. Bao2+ did not support Isin. The data indicated a U-shaped activation curve for Isin, peaking at about -10 mV. Activation of Isin occurred exponentially with a time constant of approximately 140 ms at -23 mV, becoming faster at more depolarized potentials (ca. 50 ms at -2 mV). Deactivation was slow, giving rise to tail currents lasting seconds. In some cases deactivation could be described by a single exponential process, although frequently the kinetics were more complex. Deactivation was faster at hyperpolarized potentials and sensitive to extracellular ([Ca2+]o), duration of activating voltage steps, and the degree of activation of Isin. Using CsCl-filled electrodes, the reversal potential (Erev) for Isin was -1.7 mV (SEM 3.5 mV, n = 20). Erev always corresponded to the reversal potential for gamma-aminobutyric acid-evoked currents in the same cell. In experiments in which Cs2SO4-filled electrodes were used, Erev was estimated to be -44 mV (SEM 2.3 mV, n = 9). Neither complete substitution of Nao+ with choline ions nor elevation of [K+]o 10-fold significantly affected the estimated Erev. However, substitution of Cl0- with isethionate or methanesulphonate increased the amplitude of inward currents (recorded with CsCl-filled electrodes) and shifted Erev to more depolarized potentials. The results indicate that Cl- are the primary charge carriers for this current and that Cai2+ is required for its activation, leading us to identify it as ICl(Ca).(ABSTRACT TRUNCATED AT 400 WORDS)

Genes and channels: patch/voltage-clamp analysis and single-cell RT-PCR

2000 ◽  
Vol 302 (3) ◽  
pp. 295-307 ◽  
Author(s):  
Nikolaus J. Sucher ◽  
David L. Deitcher ◽  
Deborah J. Baro ◽  
Ronald M. Harris Warrick ◽  
Elke Guenther
Keyword(s):  
Single Cell ◽  
Voltage Clamp ◽  
Rt Pcr ◽  
Voltage Clamp Analysis
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