Ion-Selectivity of Single Glutamate-Gated Channels in Locust Skeletal Muscle | Zendy

K.S. Kits | Zendy; P.N.R. Usherwood | Zendy

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Ion-Selectivity of Single Glutamate-Gated Channels in Locust Skeletal Muscle

Author(s) -

K.S. Kits,

P.N.R. Usherwood

Publication year - 1988

Publication title -

journal of experimental biology

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.367

H-Index - 185

eISSN - 1477-9145

pISSN - 0022-0949

DOI - 10.1242/jeb.138.1.499

Subject(s) - chemistry , divalent , selectivity , conductance , ion , locust , reversal potential , ammonium , ion channel , glutamate receptor , biophysics , membrane potential , patch clamp , inorganic chemistry , biochemistry , biology , receptor , botany , mathematics , organic chemistry , combinatorics , catalysis

The ion-selectivity of the extrajunctional glutamate-gated ion channel in locust extensor tibiae muscle was studied using the patch-clamp technique. The alkali metal ions Li+, Na+, K+, Rb+ and Cs+ were all highly permeant, with reversal potentials close to 0mV. Both complete and partial replacement of Na+ (180 mmoll−1 in standard saline) showed that conductance (γ) increased in the order Li+ <Na+ < Cs+ < Rb+ (approx. 70–125 pS), γK being close to γCs. The channel was impermeable to the large organic monovalent ions tetramethyl-ammonium, guanidinium and choline, and permeable to the smaller ammonium ion. Divalent cations (Ca2+ and Mg2+) did not contribute measurably to the ionic current. Indications were obtained that high concentrations of Mg2+ or Ca2+ block the channel. The results suggest that the glutamate-gated channel combines a high conductance with a restricted ion-selectivity, based on ion charge and size, the conductance being dependent on the dehydration energy of the ionic species.

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