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Pflügers Archiv - European Journal of Physiology

, Volume 413, Issue 3, pp 249–255 | Cite as

Ion permeation through hyperpolarization-activated membrane channels (Q-channels) in the lobster stretch receptor neurone

  • Å. Edman
  • W. Grampp
Excitable Tissues Cand Central Nervous Physiology

Abstract

In the lobster stretch receptor neurone it is possible to demonstrate a hyperpolarization-activated membrane current,IQ, which appears to be carried by Na+ and K+ in combination. The ion permeability of the membrane channel conducting this current (Q-channel) was investigated using conventional electrophysiological techniques including intracellular ion concentration measurements. It was found that none of the ions choline, protonated Tris, Rb+, NH 4 + , Li+, and protonated hydroxylamine was able to pass through theQ-channel which, thus, appears to be permeable to Na+ and K+ only. With increasing extracellular Na+ concentrations,IQ was increased up to a saturation level. This behaviour could be described by a one-site-two-barriers version of the Eyring rate theory, assuming that the permeant ions are turned over at specific saturable channel sites which ‘sense’ 70% of the transmembrane potential difference. With increasing extracellular K+ concentrations,IQ was increased in accordance with a simple first-order doseresponse relationship. This finding can be accounted for by assuming that K+ increases all rates of turn-over of the permeant ions at their specific sites by similar relative amounts. Changes in extracellular Na+ and K+ concentrations were found to have no effect on the gating properties of theQ-channel.

Key words

Ion permeation Ion channel Anomalous rectification Stretch receptor 

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Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • Å. Edman
    • 1
  • W. Grampp
    • 1
  1. 1.Department of Physiology and BiophysicsUniversity of LundLundSweden

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