Abstract
Potassium current inactivation and reactivation in squid axons were measured from tail current amplitudes after voltage clamp prepulses to the potassium equilibrium potential, EK, in seawater containing elevated levels of potassium ion concentration, Ko. Little or no inactivation resulted with prepulses lasting less than 100 ms. Longer pulses caused the current to inactivate in two phases, one between 0.1 and 1 s, and a second phase between 5 and 100 s. Inactivation was incomplete. The time constant of the tail current after a prepulse to EK was independent of pulse duration (0.1-120 s). Inactivation was independent of Ko (10 less than or equal to Ko less than or equal to 300 mM), and it was independent of membrane potential, V, for -40 less than or equal to V less than or equal to 0 mV. Reactivation was measured with a three-pulse protocol. The reactivation time course was sigmoidal with a delay of approximately 100 ms before significant reactivation occurred. These results were described by a model consisting of three inactivated states arranged in a linear sequence. The rate constants of the model are of the form (A + B exp (CV), or 1/(A + B exp (CV], which are required to describe the non-inactivating conductance component.
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Selected References
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- Armstrong C. M., Matteson D. R. The role of calcium ions in the closing of K channels. J Gen Physiol. 1986 May;87(5):817–832. doi: 10.1085/jgp.87.5.817. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chabala L. D. The kinetics of recovery and development of potassium channel inactivation in perfused squid (Loligo pealei) giant axons. J Physiol. 1984 Nov;356:193–220. doi: 10.1113/jphysiol.1984.sp015460. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Clay J. R. Potassium channel kinetics in squid axons with elevated levels of external potassium concentration. Biophys J. 1984 Feb;45(2):481–485. doi: 10.1016/S0006-3495(84)84172-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Clay J. R. Potassium ion accumulation slows the closing rate of potassium channels in squid axons. Biophys J. 1986 Jul;50(1):197–200. doi: 10.1016/S0006-3495(86)83452-X. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Clay J. R., Shlesinger M. F. Effects of external cesium and rubidium on outward potassium currents in squid axons. Biophys J. 1983 Apr;42(1):43–53. doi: 10.1016/S0006-3495(83)84367-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Connor J. A., Stevens C. F. Inward and delayed outward membrane currents in isolated neural somata under voltage clamp. J Physiol. 1971 Feb;213(1):1–19. doi: 10.1113/jphysiol.1971.sp009364. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dubois J. M. Evidence for the existence of three types of potassium channels in the frog Ranvier node membrane. J Physiol. 1981 Sep;318:297–316. doi: 10.1113/jphysiol.1981.sp013865. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ehrenstein G., Gilbert D. L. Slow changes of potassium permeability in the squid giant axon. Biophys J. 1966 Sep;6(5):553–566. doi: 10.1016/S0006-3495(66)86677-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., HUXLEY A. F. A quantitative description of membrane current and its application to conduction and excitation in nerve. J Physiol. 1952 Aug;117(4):500–544. doi: 10.1113/jphysiol.1952.sp004764. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Llano I., Webb C. K., Bezanilla F. Potassium conductance of the squid giant axon. Single-channel studies. J Gen Physiol. 1988 Aug;92(2):179–196. doi: 10.1085/jgp.92.2.179. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Matteson D. R., Swenson R. P., Jr External monovalent cations that impede the closing of K channels. J Gen Physiol. 1986 May;87(5):795–816. doi: 10.1085/jgp.87.5.795. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Moolenaar W. H., Spector I. Ionic currents in cultured mouse neuroblastoma cells under voltage-clamp conditions. J Physiol. 1978 May;278:265–286. doi: 10.1113/jphysiol.1978.sp012303. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nakajima S., Kusano K. Behavior of delayed current under voltage clamp in the supramedullary neurons of puffer. J Gen Physiol. 1966 Mar;49(4):613–628. doi: 10.1085/jgp.49.4.613. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schwarz J. R., Vogel W. Potassium inactivation in single myelinated nerve fibres of Xenopus laevis. Pflugers Arch. 1971;330(1):61–73. doi: 10.1007/BF00588735. [DOI] [PubMed] [Google Scholar]
- Stevens C. F. Interactions between intrinsic membrane protein and electric field. An approach to studying nerve excitability. Biophys J. 1978 May;22(2):295–306. doi: 10.1016/S0006-3495(78)85490-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Swenson R. P., Jr, Armstrong C. M. K+ channels close more slowly in the presence of external K+ and Rb+. Nature. 1981 Jun 4;291(5814):427–429. doi: 10.1038/291427a0. [DOI] [PubMed] [Google Scholar]