ATP-inhibited and Ca2+-dependent K+ channels in the soma membrane of cultured leech Retzius neurons |
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Authors: | Gudrun Frey Wolfgang Hanke Wolf-R Schlue |
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Institution: | (1) Institut für Zoologie/Lehrstuhl für Neurobiologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr 1, D-4000 Düsseldorf, FRG |
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Abstract: | The properties of one ATP-inhibited and one Ca2+-dependent K+ channel were investigated by the patch-clamp technique in the soma membrane of leech Retzius neurons in primary culture. Both channels rectify at negative potentials. The ATP-inhibited K+ channel with a mean conductance of 112 pS is reversibly blocked by ATP (K
i
= 100 m), TEA (K
i
=0.8 mm) and 10 mm Ba2+ and irreversibly blocked by 10 nm glibenclamide and 10 m tolbutamide. It is Ca2+ and voltage independent. Its open state probability (P
o) decreases significantly when the pH at the cytoplasmic face of inside-out patches is altered from physiological to acid pH values. The Ca2+-dependent K+ channel with a mean conductance of 114 pS shows a bell-shaped Ca2+ dependence of P
o with a maximum at pCa 7–8 at the cytoplasmic face of the membrane. The P
o is voltage independent at the physiologically relevant V range. Ba2+ (10 mm) reduces the single channel amplitude by around 25% (ATP, TEA, glibenclamide, tolbutamide, and Ba2+ were applied to the cytoplasmic face of the membrane).We conclude that the ATP-dependent K+ channel may play a role in maintaining the membrane potential constant—independently from the energy state of the cell. The Ca2+-dependent K+ channel may play a role in generating the resting membrane potential of leech Retzius neurons as it shows maximum activity at the physiological intracellular Ca2+ concentration.This study was supported by the Deutsche Forschungsgemeinschaft (W.-R. Schlue) and by a fellowship of the Konrad-Adenauer-Stiftung (G. Frey). We thank Dr. Draeger (Hoechst AG) for the gift of glibenclamide. The data are part of a future Ph.D. thesis of G. Frey. |
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Keywords: | Leech Potassium channel Patch clamp ATP pH Sulfonylureas |
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