Membrane currents underlying delayed rectification and pace‐maker activity in frog atrial muscle

Brown, Hilary F.; Noble, S J

doi:10.1113/jphysiol.1969.sp008940

Cited by 123 publications

(83 citation statements)

References 16 publications

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“…Changes in the kinetics of the activation of I, (Figs. 3 and 4) differ from findings in other reports in which there was no change in the kinetics (BROWN and NOBLE, 1974;PAPPANO and CARMELIET, 1979;KASS and WIEGERS, 1982). The increased Ib may have affected the actual kinetics of the activation of Ig, since it is known that during a long and strong depolarization, K accumulation occurs in the immediate exterior of the cells and I. decreases .…”

Section: Effects Of J3-agonists On the Membrane Currentscontrasting

confidence: 56%

“…The kinetics of the activation of I~ reported by BROWN and NOBLE (1974), PAPPANO andCARMELIET (1979), andWIEGERS (1982) were not altered by 3-agonists, but the present results showed an apparent change in the kinetics. It is considered that in normal solution, the increased ISi as well as the increased K accumulation caused by the increased 'b and I, affected the kinetics of I activation (Figs.…”

Section: Js-actions On Cardiac Membrane Currents 525contrasting

confidence: 39%

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.BETA.-Actions of catecholamines on the K-related currents of the bullfrog atrial muscle.

Umeno

1984

Jpn.J.Physiol

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Effects of catecholamines on K-related membrane currents in the bullfrog atrial muscle were studied under voltage clamp using the double sucrose-gap technique. Isoproterenol (10-8l0_6 M) and norepinephrine (5 x 10-6-10-5 M) induced an outward shift of the basal current level and enhanced both the background current (Ib) for hyperpolarization and the instantaneous outward current for depolarization. There was an augmentation of the slow inward current (Isi) and the delayed outward current (Ij.The augmentation of I, was induced with or without an increase in Isi, but different kinetics were involved. In the presence of Isi, j3-agonists produced a more marked augmentation of I, for the intermediate voltages of depolarization where Isi was enhanced, and Co eliminated these effects. In the absence of Isi with Co, j3-agonists elicited an enhancement of Ig; however, the enhancement was greater for larger and longer depolarizations. All these effects were absent in the presence of propranolol (5 x 10-7 M). These observations indicate that j3-agonists directly increase the background K current, and enhance the delayed outward current (Is) via two different mechanisms; one is related to the augmentation of Isi and the other is not.

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Section: Effects Of J3-agonists On the Membrane Currentscontrasting

confidence: 56%

Section: Js-actions On Cardiac Membrane Currents 525contrasting

confidence: 39%

.BETA.-Actions of catecholamines on the K-related currents of the bullfrog atrial muscle.

Umeno

1984

Jpn.J.Physiol

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“…This increase in outward current (iK) observed in adrenaline is similar to the increase in ix caused by adrenaline in the Purkinje fibre (Tsien, Giles & Greengard, 1972) and in ix,810W in the frog atrium (Brown & Noble, 1974). It is responsible for the augmented rate of repolarization of the action potential and the more negative maximum diastolic potential which adrenaline causes in the unclamped preparation (see Fig.…”

Section: Pace-maker Activity In Rabbit S-a Nodesupporting

confidence: 51%

Voltage‐clamp investigations of membrane currents underlying pace‐maker activity in rabbit sino‐atrial node.

Brown¹,

DiFrancesco²

1980

The Journal of Physiology

316

168

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SUMMARY1. Small preparations of spontaneously beating rabbit sino-atrial node have been investigated using the two micro-electrode voltage-clamp technique.2. Hyperpolarizing clamp pulses given from holding potentials of about -45 mV reveal a time-dependent change of a membrane current, if, which is shown to overlap the pace-maker range (-65 mV to -45 mV) of these preparations. 3. The changes in if are shown to be quite distinct from the de-activation of the time-dependent outward current, iK.4. The time-dependent changes of the if system increase during adrenaline application and therefore contribute to the chronotropic action of adrenaline on the heart. 5. Evidence for a link between slow inward current (i81) and time-dependent outward current (iK) in rabbit sino-atrial node is presented and assessed.

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“…Because it has been shown in the preceding results that ACh increases specifically the K conductance of atrial muscle fibre, it seemed interesting to look at whether ACh has also an action on the delayed K conductance I., 1 described by Brown & Noble (1969), Ojeda & Rougier (1974, Brown, Clark & Noble (1976). It must be noticed that the instantaneous I/V relation of I., rectifies in the inward direction (Brown, Clark & Noble, 1976;Ojeda & Rougier, unpublished).…”

Section: Methodsmentioning

confidence: 99%

The action of acetylcholine on background conductance in frog atrial trabeculae.

Garnier¹,

Nargeot²,

Ojeda³

et al. 1978

The Journal of Physiology

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The action of acetylcholine (ACh) on membrane potential and currents in frog atrial muscle has been studied with a double sucrose gap technique. The results show the following. 1. ACh induces the development of an extra current, outward at the resting potential, which is dependent on the ACh concentration. 2. The preparation does not show any sign of desensitization. 3. The reversal potential of the current induced by ACh is between 0 and 20 mV more negative than the resting potential and behaves as a K electrode. 4. The mechanism of ACh‐induced K conductance presents inward going rectification properties. 5. The delayed outward current is not affected by ACh. However the evolution of its tail current seems to indicate a process of K accumulation related to the ACh‐induced current.

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Membrane currents underlying delayed rectification and pace‐maker activity in frog atrial muscle

Cited by 123 publications

References 16 publications

.BETA.-Actions of catecholamines on the K-related currents of the bullfrog atrial muscle.

.BETA.-Actions of catecholamines on the K-related currents of the bullfrog atrial muscle.

Voltage‐clamp investigations of membrane currents underlying pace‐maker activity in rabbit sino‐atrial node.

The action of acetylcholine on background conductance in frog atrial trabeculae.

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