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A patch clamp study of γ‐aminobutryic acid (GABA)‐induced macroscopic currents in rat melanotrophs in cell culture
Author(s) -
Kehl Steven J.,
Hughes David,
McBurney Robert N.
Publication year - 1987
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1987.tb11359.x
Subject(s) - chloride channel , bicuculline , gabaa receptor , reversal potential , biophysics , patch clamp , chemistry , chloride , gaba receptor antagonist , gamma aminobutyric acid , gaba receptor , picrotoxin , voltage clamp , extracellular , receptor , membrane potential , medicine , endocrinology , biochemistry , biology , organic chemistry
1 The macroscopic currents induced in cultured rat melanotrophs by exogenous γ‐aminobutyric acid (GABA) were analysed using the patch clamp recording technique. 2 Using various concentrations of intra‐and extracellular chloride it was demonstrated that the conductance activated by GABA was chloride selective. Since these currents were blocked with bicuculline and enhanced with chlordiazepoxide the involvement of GABA A receptors similar to those in the CNS is indicated. 3 When chloride was symmetrically distributed across the membrane the voltage/current relationship was linear; pronounced rectification of GABA mediated currents was evident when there was an asymmetrical distribution of chloride. 4 With concentrations of GABA greater than 10 μ m a fading of the current was seen during prolonged (5–10 s) applications. This effect appeared to be due to a decline of conductance rather than a shift of the chloride equilibrium potential. 5 Values for the Hill coefficient derived from dose‐response curves suggested that the binding of 2 molecules of GABA to the receptor is required for the activation of the chloride channel. 6 There was no indication of a direct, GABA B receptor‐mediated change of conductance.