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Selectivity and patch measurements of A‐current channels in Helix aspersa neurones.
Author(s) -
Taylor P S
Publication year - 1987
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1987.sp016623
Subject(s) - conductance , current (fluid) , chemistry , helix (gastropod) , selectivity , reversal potential , permeability (electromagnetism) , membrane potential , ion channel , biophysics , membrane , patch clamp , biology , condensed matter physics , physics , biochemistry , thermodynamics , ecology , receptor , snail , catalysis
1. The ionic selectivity of A‐current K+ channels has been measured in single Helix aspersa neurones by recording the reversal potential shift in test solutions containing various monovalent cations. 2. The A‐current channel is permeable to Tl+, K+, Rb+, NH4+ and Cs+. The channels may also be sparingly permeable to Na+ and Li+. Organic cations have an apparent small permeability as judged from their reversal potentials, but this may be an artifact of K+ accumulation. 3. A large patch electrode (3 microns tip) isolated a region that appeared to contain only A‐current channels. This may indicate that A‐current channels are found in the membrane as rafts of at least 3 microns in diameter. 4. The single‐channel conductance calculated from single‐channel current steps was 14 pS.