Kinetic Modulation by GABAergic Agents of High‐ and Low‐Affinity Binding of [3H]Methyl β‐Carboline‐3‐Carboxylate

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Abstract: The kinetics of dissociation of [3H]methyl β‐carboline‐3‐carboxylate (β‐CCM) binding was studied in a synaptosomal membrane preparation of rat cerebral cortex. Dissociation was biphasic: a faster phase (10–30% contribution) was followed by a slower phase. Picrotoxin pre‐treatment at 22°C enhanced the equilibrium binding of [3H]β‐CCM. The half‐life of the slower phase of β‐CCM dissociation (tII1/2) was increased by 60 μM picrotoxin from 1.7 min to 3.3 min. The dissociation of [3H]β‐CCM was identical when initiated by an excess of either diazepam or β‐CCM. Quasi‐equilibrium Scatchard analysis of [3H]β‐CCM binding was performed by a kinetic separation of the rapid and slow phases of dissociation. The slow and rapid phases represented β‐CCM binding sites of high and low affinity, respectively. The dissociation of [3H]β‐CCM (control tII1/2= 2.0 min) was decelerated by the γ‐aminobutyric acid (GABA) antagonist 3–α‐hydroxy‐16‐imino‐5β‐17‐azaandrostan‐11‐one (R 5135) (tII1/2= 2.5 min) and accelerated by GABA (tII1/2= 1.6 min). GABA inhibited both high‐ and low‐affinity β‐CCM bindings.

Original languageEnglish
Pages (from-to)1859-1864
Number of pages6
JournalJournal of neurochemistry
Issue number6
Publication statusPublished - Jun 1988


  • Benzodiazepine receptor heterogeneity
  • GABAergic modulation
  • Kinetics of receptor binding
  • Picrotoxin
  • β‐Carboline inverse agonist
  • β‐Carboline‐3‐carboxylic acid [H]methyl ester

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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