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Updated: May 6, 2026

Whole-cell Patch-clamp Recordings for Electrophysiological Determination of Ion Selectivity in Channelrhodopsins
Published on: May 22, 2017
Cation selectivity of the resting membrane of squid axon
S Hagiwara1, D C Eaton, A E Stuart
1Department of Physiology, U.C.L.A., 90024, Los Angeles, California.
Abstract:
Permeability constant ratios among monovalent cations were studied in the resting membrane of a giant axon of a Pacific squid,Loligo opalescens, by observing the relationship between the membrane potential and the ion concentration.The average permeability ratios are: Tl, 1.8; K, 1.0; Rb, 0.72; Cs, 0.16; Na, <0.08; Li, <0.08. These permeability ratios suggest that neither valinomycin nor nonactin are adequate models for the sites producing the resting permeability in the axonal membrane.Cyclic polyetherbis(t-butyl cyclohexyl) 18-crown-6 does not increase the permeability ratioP Cs/P K except when applied at concentrations (5×10(-5) M) at which the surfactant properties of this molecule may become significant.
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