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Bicuculline‐ and Baclofen‐Insensitive γ‐Aminobutyric Acid Binding to Rat Cerebellar Membranes
Author(s) -
Drew Colleen A.,
Johnston Graham A. R.
Publication year - 1992
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1992.tb09366.x
Subject(s) - muscimol , bicuculline , baclofen , aminobutyric acid , gabaa receptor , gabab receptor , chemistry , binding site , gaba receptor antagonist , gamma aminobutyric acid , biochemistry , gaba receptor , antagonist , cerebellum , agonist , medicine , endocrinology , receptor , biology
Up to 60% of γ‐[ 3 H]aminobutyric acid ([ 3 H]GABA) bound specifically to rat cerebellar membranes in the absence of Ca 2+ was insensitive to the GABA A antagonist bicuculline and to the GABA B agonist baclofen. This indicates that a significant component of specifically bound [ 3 H]GABA is associated with non‐GABA A , non‐GABA B binding sites. The presence of this binding component appeared seasonal, peaking in the month of September (early spring) each year over a 4‐year period. The calcium independence and bicuculline and baclofen insensitivity of the binding indicate that this binding is not to the classical GABA A and GABA B binding sites. High concentrations of muscimol and isoguvacine inhibited non‐GABA A , non‐GABA B binding. Scatchard analysis of the non‐GABA A , non‐GABA B binding sites indicated two kinetic components: K DI = 42 nM and K D2 = 9.2 μM; B maxi = 1.6 pmol/mg of protein and B max2 = 28 pmol/mg of protein.