The effects of stimulation rate on calcium‐dependent action potentials recorded from chick embryo heart cell aggregates.

MacKenzie, Eric T.; Standen, N B

doi:10.1113/jphysiol.1982.sp014096

Cited by 10 publications

(7 citation statements)

References 31 publications

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“…The experimental methods and techniques have been described in the previous paper (Campbell, Giles & Shibata, 1988 Lee & Fozzard, 1975;Miura, Hoffman & Rosen, 1977;Scheid & Fay, 1980 Mg2+ or Na+ produced no significant shifts in Erev These findings are consistent with our previous results showing that 'non-specific' monovalent cation-mediated inward currents through Ca21 channels in bull-frog atrium can be recorded only when [Ca2+] Reuter & Scholz, 1977;Akiyama & Fozzard, 1979;Mackenzie & Standen, 1982;Lee & Tsien, 1984). (Reuter & Scholz, 1977;Lee & Tsien, 1982 that the outward currents recorded positive to Erev in bull-frog atrial cells (Hume & Giles, 1983;Campbell et al 1988c) are carried mainly by K+ ions flowing outward through activated Ca2+ channels.…”

Section: Electrophysiological Method8 and Data Analyetssupporting

confidence: 82%

“…reversal potential data can be fitted with a PK/PCa = 0-005220. Akiyama & Fozzard, 1979), and Ca2+ (508%): Na+ (492°%) (Mackenzie & Standen, 1982). Therefore, it has often been assumed that a very significant portion of 'ICa in cardiac tissue is carried by monovalent ions.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, using the criteria that have been used by previous investigators it is clear that relatively large positive values of V' do not describe the data well when a correct explicit equation for Erev is used (cf. Meves & Vogel, 1973;Reuter & Scholz, 1977;Akiyama and Fozzard, 1979;Mackenzie & Standen, 1982;Lee & Tsien, 1982 Hagiwara, 1975). Fig.…”

Section: Electrophysiological Method8 and Data Analyetsmentioning

confidence: 99%

“…Reuter & Scholz, 1977;Akiyama & Fozzard, 1979;Mackenzie & Standen, 1982;Lee & Tsien, 1984). However, careful review of these papers reveals that the existing quantitative expressions for the reversal potential of ICa in cardiac tissue (developed from simple constant field theory) require further clarification(s) and correction(s).…”

Section: Reversal Potential Of Ica In Heartmentioning

confidence: 99%

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Reversal potential of the calcium current in bull‐frog atrial myocytes.

Campbell

Giles

Hume

et al. 1988

The Journal of Physiology

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SUMMARY1. Voltage clamp recordings of the calcium current (ICa) in single myocytes which were enzymatically isolated from bull-frog atrium show that a genuine reversal of the current flowing through Ca2" channels can be recorded (cf. Reuter & Scholz, 1977;Lee & Tsien, 1982Campbell, Giles & Shibata, 1988c 4. The apparent reversal potential is analysed using a form of the constant field equation which has been modified to include (i) simultaneous monovalent and divalent cation movements and (ii) the presence of a surface potential (V'). This equation can be solved to yield an explicit expression for Erev. The effects of V' on apparent permeability ratios for the Ca2+ channel Erev are demonstrated.5. In combination, our experimental results and calculations suggest that: (i) previous estimates of V' which were used to describe permeability (P) ratios of Caa2+ channels in various cardiac preparations may be in error, (ii) in normal [Ca2+]0 the PNa/PCa ratio is very small, and (iii) PCa/PK must be greater than 1000. An analysis of the relative selectivity of the channel for divalent cations compared to K+ shows that PCa > Psr > PBa, assuming that PK remains the same after the divalent substitutions.6. The Ca21 channel in bull-frog atrial cells is thus much more selective for Ca21 ions than had previously been estimated; in particular, inward flow of monovalent

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Section: Electrophysiological Method8 and Data Analyetssupporting

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Electrophysiological Method8 and Data Analyetsmentioning

confidence: 99%

Section: Reversal Potential Of Ica In Heartmentioning

confidence: 99%

See 2 more Smart Citations

Reversal potential of the calcium current in bull‐frog atrial myocytes.

Campbell

Giles

Hume

et al. 1988

The Journal of Physiology

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“…Mean burst length = 48 s. mechanisms, e.g. frequencyor Ca2+-dependent inactivation of K+ currents (Aldrich, Getting & Thompson, 1979;Eckert & Lux, 1977;Alkon, Shoukimas & Heldman, 1982;Mackenzie & Standen, 1982).…”

Section: Discussionmentioning

confidence: 99%

Activity dependence of action potential duration in rat supraoptic neurosecretory neurones recorded in vitro.

Bourque¹,

Renaud²

1985

The Journal of Physiology

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SUMMARY1. Action potential durations, measured at one-third peak amplitude, were examined during intracellular recordings in 134 supraoptic nucleus neurones maintained in vitro in perfused hypothalamic explants.2. Spike durations ranged between 1-2 and 3-9 ms and were dependent on firing frequency. Shortest measurements (1 P74 + 0-03 ms; mean + S.E. ofmean) were obtained during relative quiescence, i.e. < 0'5 Hz. A gradual increase in firing frequency through continuous injection of depolarizing current prolonged spike duration, with maximum levels (2-68 + 0-05 ms) achieved at 20 Hz. When interspike interval variability was eliminated and firing was more precisely regulated by brief 15-20 ms intracellular current pulses given at pre-determined frequencies, a proportional relationship between increasing spike duration and firing frequency was retained but the change in spike duration at frequencies between 2 and 10 Hz was less pronounced.3. Once action potentials had achieved the long duration configuration, their return to the shorter duration took place gradually during any succeeding silent interval with a time constant of 4-9 s. 4. Action potential broadening occurred progressively and was most pronounced at the onset of spontaneous or current-induced bursts. In thirty-six phasically active neurones, spike broadening at the onset of a burst was concurrent with the presence of 5-10 consecutive short (< 100 ms) interspike intervals; thereafter, despite a greater than 50 % reduction in firing frequency, action potential durations remained prolonged throughout the burst.5. In all of nineteen cells tested, frequency-dependent changes in spike duration were reversibly decreased or blocked by Cd2+, Co2+ and Mn2+, or when CaCl2 was exchanged for equimolar amounts of EGTA in the perfusion medium.6. These observations indicate that a Ca2+ conductance contributes to frequencyand firing-pattern-dependent changes in spike duration in rat supraoptic nucleus neurones.

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Saturation characteristics, Ca2+ ions and drug-induced block of cardiac Isi-mediated action potentials

Kohlhardt

1983

Naunyn-Schmiedeberg's Arch. Pharmacol.

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The effects of stimulation rate on calcium‐dependent action potentials recorded from chick embryo heart cell aggregates.

Cited by 10 publications

References 31 publications

Reversal potential of the calcium current in bull‐frog atrial myocytes.

Reversal potential of the calcium current in bull‐frog atrial myocytes.

Activity dependence of action potential duration in rat supraoptic neurosecretory neurones recorded in vitro.

Saturation characteristics, Ca2+ ions and drug-induced block of cardiac Isi-mediated action potentials

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