ATP-sensitive and Ca-activated K channels in vertebrate axons: novel links between metabolism and excitability.
Two types of metabolically regulated K channels have been identified for the first time in enzymatically demyelinated fibres of amphibian sciatic nerve using the patch-clamp technique. A maxi K channel with a single-channel conductance of 132 pS (105 mM K on both sides of the membrane, 15 degrees C) is activated both by micromolar concentrations of internal Ca and by depolarization. A second type of K channel with a conductance of 44 pS is inhibited by intracellular adenosine 5'-triphosphate (ATP) with a half-maximal inhibitory concentration (IC50) of 35 microM. It is blocked by submicromolar concentrations of external glibenclamide. Both channels are sensitive to external tetraethylammonium chloride (IC50 = 0.2 mM for the maxi K channel and 4.2 mM for the ATP-sensitive channel). They may be part of a complex feedback system regulating axonal excitability under various metabolic conditions.
Jonas
P
P
Physiologisches Institut, Justus-Liebig-Universität, Giessen, Federal Republic of Germany.
Koh
D S
DS
Kampe
K
K
Hermsteiner
M
M
Vogel
W
W
D000200:Action Potentials; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D014982:Xenopus laevis
D015221:Potassium Channels; D000644:Quaternary Ammonium Compounds; D000255:Adenosine Triphosphate; C027917:tetramethylammonium; D002118:Calcium