Existence and role of a slow inward current during the frog atrial action potential

Rougier, O; Vassort, Guy; Garnier, D; Gargouïl, Y.M.; Coraboeuf, E

doi:10.1007/bf00587018

Cited by 425 publications

(187 citation statements)

References 30 publications

Supporting

Mentioning

174

Contrasting

Order By: Relevance

“…in order to block the fast initial current (Rougier, Vassort, Garnier, Gargouil & Coraboeuf, 1969). In a recent paper Connor, Barr & Jackobsson (1975) have reported that this concentration of TTX fails to abolish the fast inward current completely in frog atrial traceculae.…”

Section: Methodsmentioning

confidence: 98%

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

Garnier¹,

Nargeot²,

Ojeda³

et al. 1978

The Journal of Physiology

View full text Add to dashboard Cite

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.

show abstract

Section: Methodsmentioning

confidence: 98%

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

Garnier¹,

Nargeot²,

Ojeda³

et al. 1978

The Journal of Physiology

View full text Add to dashboard Cite

show abstract

“…Recent investigations on the mechanisms underlying the action potential of heart tissues have lead to the separation of the total inward current in two components (ROUGIER et al, 1969 ;TARR, 1971). A fast inward current, which accounts for the rapid phase of the upstroke of the action potential; and a slow inward current responsible for the slow phase of depolarization and the plateau of myocardial action potentials (CARMELIET and VEREECKE, 1969;BEELER and REUTER, 1970).…”

Section: Discussionmentioning

confidence: 99%

Denervated Muscle: Rate of Propagation and Effects of Manganese Ions and Glycerol on the Fibrillatory Activity of Frog Semitendinosus

López

1979

Jpn.J.Physiol

View full text Add to dashboard Cite

Denervated frog's semitendinosus muscles were studied. Fibrillation potentials generate propagated spikes which are conducted at a rate similar to that calculated for innervated muscles. The twitch tension per unit area was similar in denervated and innervated single fibres; the average value corresponded with values reported in the literature for fibres stimulated at 125/sec. Manganese ions (1-3 mM), selectively inhibit fibrillation potentials and have no appreciable effect upon evoked spikes. Mn2+ also inhibits (40-50%) the twitch responses and abolishes the resting tension of muscle fibres. The latter effects were observed in denervated as well as in innervated preparations when the fibres studied belonged to fascicles located at the site of entrance of the nerve. Disruption of the transverse tubular system by glycerol treatment does not interfere with the generation of fibrillation potentials, although the effects on twitching are similar to those reported in the literature. A possible mechanism is proposed to explain the generation of fibrillation potentials in frog denervated muscles.The fibrillatory activity of the denervated semitendinosus muscle of the frog has been described in a previous paper (LOPEZ, 1978). It was mentioned, as a possibility to explain the poor tension development occasionally observed in that study, that fibrillation potentials might not give rise to propagated electrical activity. It was also considered that the transverse tubular system (TTS), a possible site of origin of the discrete depolarizations found in denervated mammalian muscles (PURVES and SAKMANN, 1974;SMITH and THESLEFF, 1976), could provide an explanation to the fact that, in the frog, it is possible to obtain spontaneous depolarizations, and repetitive firing, from any spot along the muscle length.On these bases, the present study was aimed at obtaining further information related to the propagation of fibrillation potentials and inquiring further about the role the TTS may possibly play in the genesis of the electrical fibrillatory activity. The results obtained during the study are described in this paper.

show abstract

“…Mn ion is known to block reversibly the ionic channel for inward Ca current in various excitable tissues including myocardial cell (HAGIWARA and NAKAJIMA, 1966;ROUGIER et al, 1969;CHIARANDINI et al, 1970;BAKER et al, 1971). In the experiment shown in Fig.…”

Section: Inhibitory Action Of Mn Ion On the Mechanical Response In LImentioning

confidence: 99%

Contractility of the Frog Ventricular Myocardium in Sodium-free Lithium Solution

Kawata

1979

Jpn.J.Physiol

View full text Add to dashboard Cite

The effects of Na-free Li solution on the electrical and mechanical activities were examined in a bullfrog's ventricular strip. The action potential showed a triphasic change during Na-free perfusion : the initial decrease in the overshoot and duration, the secondary restoration and the gradual decrease in the membrane potential. The twitch contraction also changed in a triphasic manner : the initial rapid decrease with a transient development of contracture and the secondary slow decrease followed by a partial recovery. A negative staircase, which was accompanied by full-sized twitch contractions, was induced by lowering the stimulation rate in this medium, indicating an involvement of some intracellular Ca releasing sites for activating the well-maintained contractile proteins. When CaCl2 was omitted during Na-free Li perfusion the twitch decreased only slightly down to 71.8 % whereas in Na-containing medium it decreased to 11.9 %. The sensitivity of twitch to the external Ca was thus greatly diminished in the Na-free condition. A fairly large contracture could be elicited by high K solution in Ca-free Li solution even after a prolonged Ca-free perfusion. Modification of the action potential by passing a hyperpolarizing current did not affect the twitch occurring in the Li solution, in contrast to its marked effect on the muscle perfused with normal Ringer. From these results it is concluded that the twitch is activated mainly by Ca released from some intracellular site in the Na-free Li solution. The inhibitory effect of Mn on this contraction was discussed in relation to its intracellular action.Previous studies have shown that the myocardial contractile force depends not only on the Ca concentration but also the Na concentration in the medium in both amphibian and mammalian hearts (WILBRANDT and KOLLER, 1948;LUTTGAU and NIEDERGERKE, 1958;REITER, 1964). Thus it has been established that the maximum height of twitch contraction as well as potassium contracture varies with the ratio of [Ca]o/[Na]2o. Later, the existence of a carrier-mediated

show abstract

Existence and role of a slow inward current during the frog atrial action potential

Cited by 425 publications

References 30 publications

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

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

Denervated Muscle: Rate of Propagation and Effects of Manganese Ions and Glycerol on the Fibrillatory Activity of Frog Semitendinosus

Contractility of the Frog Ventricular Myocardium in Sodium-free Lithium Solution

Contact Info

Product

Resources

About