The Journal of Membrane Biology

, Volume 89, Issue 2, pp 139–152 | Cite as

Inward membrane current inChara inflata: I. A voltage- and time-dependent Cl component

  • S. D. Tyerman
  • G. P. Findlay
  • G. J. Paterson


An inward current which increases in magnitude over a period of seconds is activated when the membrane ofChara inflata (a green alga) in a K+-conductive state is hyperpolarized by a voltage clamp. The peak current and the half-time of activation are exponentially dependent on membrane potential difference. It was found by using an external Cl electrode that the component exponentially dependent on potential was due to an efflux of Cl. The measured current-voltage curves and the kinetics of deactivation of the current showed that other time-dependent components contributed to the net inward current. The “punchthrough” theory of Coster (Biophys. J.5:669–686, 1965) does not adequately explain the inward current since a “punchthrough potential” could not be obtained, and the inward current was distinctly time dependent. The voltage and time dependence of the inward current strongly suggests that the Cl efflux activated by hyperpolarization is through voltage-gated channels which open more frequently as the membrane is hyperpolarized.

Key Words

Cl channels ion channels Chara inflata membranes punchthrough 


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Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • S. D. Tyerman
    • 1
  • G. P. Findlay
    • 1
  • G. J. Paterson
    • 1
  1. 1.School of Biological SciencesThe Flinders University of South AustraliaBedford Park

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