Changes in the intracellular concentration of free calcium ions in a pace‐maker neurone, measured with the metallochromic indicator dye arsenazo III.

Gorman, A. L. F.; Thomas, Mandy

doi:10.1113/jphysiol.1978.sp012194

Cited by 222 publications

(149 citation statements)

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“…1 C). The effects of external TEA on pacemaker activity and the sizable increase in internal Ca 2+ concentration that occurs in cell R-15 during the prolonged action potential have been shown previously (Gorman and Thomas, 1978). The effect of TEA on the action potential is quite different from the approximately 2.2-fold increase in duration produced by 4-aminopyridine (see Fig.…”

Section: Effects Of External Tea On the Action Potentialmentioning

confidence: 63%

“…This current must be balanced by outward currents flowing through unblocked K + and leakage channels. It has been shown (Gorman and Thomas, 1978) that in the presence of 50 mM external TEA there can be an increase as great as 13-fold in the intracellular Ca 2+ concentration at the end of a prolonged action potential for…”

Section: Effects (External Tea On the Ca2+-activated K + Currentmentioning

confidence: 99%

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Effects of tetraethylammonium on potassium currents in a molluscan neurons.

Hermann¹,

Gorman²

1981

The Journal of General Physiology

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186

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The effects of tetraethylammonium (TEA) on the delayed K + current and on the Ca2+-activated K + current of the Aplysia pacemaker neurons R-15 and L-6 were studied. The delayed outward K + current was measured in Ca2+-free ASW containing tetrodotoxin (TTX), using brief depolarizing clamp pulses. External TEA blocks the delayed K + current reversibly in a dosedependent manner. The experimental results are well fitted with a MichaelisMenten expression, assuming a one-to-one reaction between TEA and a receptor site, with an apparent dissociation constant of 6.0 raM. The block depends on membrane voltage and is reduced at positive membrane potentials. The Ca 2+-activated K + current was measured in Ca2+-free artificial seawater (ASW) containing TTX, using internal Ca 2+ ion injection to directly activate the K + conductance. External TEA and a number of other quaternary ammonium ions block the Ca2+-activated K + current reversibly in a dose-dependent manner. TEA is the most effective blocker, with an apparent dissociation constant, for a one-to-one reaction with a receptor site, of 0.4 raM. The block decreases with depolarization. The Caa+-activated K + current was also measured after intracellular iontophoretic TEA injection. Internal TEA blocks the Ca2+-activated K + current (but the block is only apparent at positive membrane potentials), is increased by depolarization, and is irreversible. The effects of external and internal TEA can be seen in measurements of the total outward K + current at different membrane potentials in normal ASW.The quaternary ammonium ion, tetraethylammonium (TEA), blocks voltagedependent potassium channels in nerve and muscle cells (Hagiwara

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Section: Effects Of External Tea On the Action Potentialmentioning

confidence: 63%

Section: Effects (External Tea On the Ca2+-activated K + Currentmentioning

confidence: 99%

Effects of tetraethylammonium on potassium currents in a molluscan neurons.

Hermann¹,

Gorman²

1981

The Journal of General Physiology

Self Cite

186

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show abstract

“…lOB); from the slope of this relation the fractional inactivation, m, could be determined. In this case, the (Gorman & Thomas, 1978;Ahmed & Connor, 1979). Both Ca2+ current and the extent of INa,cAMP inactivation peak near + 50 mV, and decline with depolarization.…”

Section: Introductionmentioning

confidence: 99%

Co‐regulation of cAMP‐activated Na+ current by Ca2+ in neurones of the mollusc Pleurobranchaea.

Huang

Gillette

1993

The Journal of Physiology

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“…Application of this method to Ca-titration curves of arsenazo III and antipyrylazo III showed clear evidence of multiple types of calcium complexing for both dyes (4,5). The possibility of multiple complex formation between Ca2+ and arsenazo III has been previously raised (13), but analytical methods used by other investigators gave results compatible with assuming only a 1: 1 calcium-complexing model for arsenazo III (2,6).…”

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confidence: 74%

Arsenazo I and tetramethylmurexide as optical calcium indicators

Dorogi

Santarius

Neumann

1982

Analytical Biochemistry

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Calcium-binding stoichiometry, dissociation equilibrium constants at zero ionic strength @Lo), and molar extinction difference coefficients (At,) at the wavelength )r of the metallochromic indicators arsenazo I (ArsI) and tetramethylmurexide (TMX) were reevaluated with a computerized method based on mass conservation and thermodynamic consistency checks. This new method is shown to provide a more critical assessment of the assumed calcium-dye complexing model than is afforded by the commonly used reciprocal-plot method. The analyses of spectrophotometric Ca titrations confirm that both dyes form only 1: 1 complexes in aqueous solution. For TMX, R" = 1.3 X lOA3 hp and At&,, = 1.5 X I@ M-' cm-'; for Arsl, R" = 5.8 X 10el M and A6562 = 1.8 X 104 M-' cm-' at pH '7.0 and T = 293OK. The discriminatory power of the analytical method is demonstrated by comparison of these results with those found for a different dye, arsenazo III, which complexes Ca in l:l, 1:2, and 2:l forms.

show abstract

Changes in the intracellular concentration of free calcium ions in a pace‐maker neurone, measured with the metallochromic indicator dye arsenazo III.

Cited by 222 publications

References 33 publications

Effects of tetraethylammonium on potassium currents in a molluscan neurons.

Effects of tetraethylammonium on potassium currents in a molluscan neurons.

Co‐regulation of cAMP‐activated Na+ current by Ca2+ in neurones of the mollusc Pleurobranchaea.

Arsenazo I and tetramethylmurexide as optical calcium indicators

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