Characterization of single non-inactivating potassium channels in primary neuronal cultures of Drosophila.
Permeability and gating properties of single, non-inactivating, K+ channel currents in cultured Drosophila neurons were studied using the gigaohm-seal patch-clamp technique. The non-inactivating K+ currents were activated by depolarizing the membrane to -30 mV or to more positive potentials. The slope conductance of the channel was estimated to be 17.6 +/- 3.70 pS when the cytoplasmic side of the inside-out membrane patch was perfused with solutions containing 145 mmoll-1 K+. The single-channel conductance was temperature-sensitive, with a Q10 of 1.44 between 10 and 20 degrees C. Single-channel currents could be recorded when the cytoplasmic K+ was replaced with NH4+, Rb+ or Na+, but not with Cs+. The conductance ratio of the channel for these cations was: K+ (1) greater than NH4+(0.53) greater than Rb+ (0.47) greater than Na+ (0.44). Tetraethylammonium (TEA+) ions applied at a concentration of 10 mmoll-1 to the cytoplasmic side of the membrane increased the frequency of 'blank' traces which contained no channel openings during repetitive depolarization. In addition, single-channel amplitude was reduced by about 20%. The open-time distribution was fitted by a single exponential function, whereas the closed-time distribution required a three-exponential fit. Permeability and gating properties of single, non-inactivating K+ channel currents in neurons of eag, a mutant which has defects in the delayed rectifier K+ channel, were indistinguishable from those recorded from wild-type neurons.
Yamamoto
D
D
Laboratory of Neurophysiology, Mitsubishi-Kasei Institute of Life Sciences, Tokyo, Japan.
Suzuki
N
N
D000200:Action Potentials; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D004331:Drosophila melanogaster / Q000502:physiology*; D009431:Neural Conduction; D009474:Neurons / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds