Currents related to the sodium-calcium exchange in squid giant axon.

Biochimica Et Biophysica Acta
C CaputoR DiPolo

Abstract

We report the measurement of a Cai-activated membrane current in dialyzed squid axon under membrane potential control with a low-noise voltage clamp. Two additional voltage clamp systems were used to clamp the external guard plates to a value that prevented the establishment of potential differences between the central and lateral compartments of the experimental chamber. This reduced to a minimum the contribution of membrane currents generated at the axon ends to the current measured in the central pool. This latter current was reduced by using internal and external solutions designed to diminish at a maximum membrane currents, while maintaining the conditions for optimal operation of the Na+-Ca2+ exchange. Thus TTX was used to block Na+ channels and prolonged exposure to K+-free media was used to eliminate K+ conductance. The maximum concentration of external sodium was 200 mM. The addition of fixed amounts of free ionic calcium to the internal solution, activated a current whose direction and magnitude depended on the thermodynamic driving forces for calcium and sodium. When the experimental conditions determined an inwardly directed current, this depended on the presence of external sodium, and lithium could not substitute ...Continue Reading

References

Dec 1, 1984·The Journal of General Physiology·R DiPolo, L Beaugé
Oct 18, 1984·Nature·K W Yau, K Nakatani

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Citations

Jan 1, 1991·Pharmacology & Therapeutics·L MissiaenR Casteels
Sep 17, 2002·Progress in Biophysics and Molecular Biology·Reinaldo DiPolo, Luis Beaugé
Jan 1, 1993·The Journal of Pharmacy and Pharmacology·J CortijoE Morcillo
Aug 4, 2007·Progress in Neurobiology·Tamás L Török
Dec 24, 2005·Physiological Reviews·Reinaldo DiPolo, Luis Beaugé
Jul 3, 1999·Physiological Reviews·M P Blaustein, W J Lederer
Jan 1, 1992·Glia·M H Kim-LeeA J Yates

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