ATP-inhibited and Ca(2+)-dependent K+ channels in the soma membrane of cultured leech Retzius neurons.
The properties of one ATP-inhibited and one Ca(2+)-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 (Ki = 100 microM), TEA (Ki = 0.8 mM) and 10 mM Ba2+ and irreversibly blocked by 10 nM glibenclamide and 10 microM tolbutamide. It is Ca2+ and voltage independent. Its open state probability (Po) decreases significantly when the pH at the cytoplasmic face of inside-out patches is altered from physiological to acid pH values. The Ca(2+)-dependent K+ channel with a mean conductance of 114 pS shows a bell-shaped Ca2+ dependence of Po with a maximum at pCa 7-8 at the cytoplasmic face of the membrane. The Po 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 Ca(2+)-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.
Frey
G
G
Institut für Zoologie/Lehrstuhl für Neurobiologie, Heinrich-Heine-Universität Düsseldorf, FRG.
Hanke
W
W
Schlue
W R
WR
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002478:Cells, Cultured; D002586:Cesium / Q000494:pharmacology; D004558:Electric Stimulation; D005905:Glyburide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007865:Leeches / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000737:chemistry / Q000166:cytology* / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014044:Tolbutamide / Q000494:pharmacology
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D002586:Cesium; D001464:Barium; D019789:Tetraethylammonium; D000255:Adenosine Triphosphate; D014044:Tolbutamide; D005905:Glyburide; D002118:Calcium