Abstract
The effect of phloretin, a dipolar organic compound, on single potassium channel currents of myelinateed nerve fibres of Xenopus laevis has been investigated, using inside-out patches prepared by the method of Jonas et al. (1989). The I channel, a potential dependent K channel with intermediate deactivation kinetics, was reversibly blocked by 20 µM phloretin applied on the inside; the block was strongest at negative membrane potentials and less pronounced at positive potentials. Phloretin shifted the curve relating open probability to membrane potential towards more positive potentials and reduced its slope and maximum. This confirms previous findings on the effect of phloretin on the voltage dependence of the fast macroscopic K conductance. Single channel conductance and deactivation kinetics were not altered by phloretin.
Similar content being viewed by others
References
Dubois JM (1981) Evidence for the existence of three types of potassium channels in the frog Ranvier node membrane. J Physiol 318:297–316
Fenwick EM, Marty A, Neher E (1982) Sodium and calcium channels in bovine chromaffin cells. J Physiol 331:599–635
Gola M, Ducreux C, Chagneux H (1990) Ca2+-activated K+ current involvement in neuronal function revealed by in situ single channel analysis in Helix neurones. J Physiol 420:73–109
Jonas P, Bräu ME, Hermsteiner M, Vogel W (1989) Single-channel recording in myelinated nerve fibers reveals one type of Na channel but different K channels. Proc Natl Acad Sci USA 867:7238–7242
Jonas P, Koh D-S, Kampe K, Hermsteiner M, Vogel W (1991) ATP-sensitive and Ca-activated potassium channels in vertebrate axons: Novel links between metabolism and excitability. Pflügers Arch 418:68–73
Klusemann J, Koh D-S (1991) Phloretin, a dipolar organic compound, strongly affects the potassium channels of the frog myelinated nerve fibre. 19th Neurobiology Conference Göttingen (abstr) 426
Klusemann J, Meves H (1991) Phloretin affects the fast potassium channels in frog nerve fibres. Eur Biophys J 20:79–86
Klusemann J, Meves H (1992) The effect of phloretin on single potassium channels of nerve fibres of Xenopus laevis. Pflügers Arch 420 [Suppl 1]: R32
Nagy K (1987) Evidence for multiple open states of sodium channels in neuroblastoma cells. J Membrane Biol 96:251–262
Nagy K, Kiss T, Hof D (1983) Single Na channels in mouse neuroblastoma cell membrane. Indications for two open states. Pflügers Arch 399:302–308
Plant TD (1986) The effect of rubidium ions on components of the potassium conductance in the frog node of Ranvier. J Physiol 375:81–105
Spires S, Begenisich T (1989) Pharmacological and kinetic analysis of K channel gating currents. J Gen Physiol 93:263–283
Strichartz GR, Oxford GS, Ramon F (1980) Effects of the dipolar form of phloretin on potassium conductance in squid giant axons. Biophys J 31:229–246
Author information
Authors and Affiliations
Additional information
Offprint requests to: Correspondence to: H. Meves
Rights and permissions
About this article
Cite this article
Klusemann, J., Meves, H. The effect of phloretin on single potassium channels in myelinated nerve. Eur Biophys J 21, 93–97 (1992). https://doi.org/10.1007/BF00185424
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00185424