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GABA receptor-mediated modulation of 3H-diazepam binding in rat cortex
European Journal of Pharmacology
|July 1, 1979
Summary
Endogenous GABA influences 3H-diazepam binding assays by affecting binding affinity and capacity. Bicuculline and bicucine also impact binding, suggesting interactions at the GABA binding site.
Area of Science:
- Neuroscience
- Pharmacology
Background:
- 3H-diazepam binding is a key assay in neuroscience.
- The influence of endogenous gamma-aminobutyric acid (GABA) on this assay is not fully understood.
Purpose of the Study:
- To investigate the effects of GABA, bicuculline, and bicucine on 3H-diazepam binding in rat cortex membrane preparations.
- To determine if endogenous GABA affects assay results.
Main Methods:
- Utilized three rat cortex membrane preparations: crude synaptosomal fraction, repeatedly washed membranes, and washed, frozen, and thawed membranes.
- Assessed the impact of GABA, bicuculline, and bicucine on 3H-diazepam binding parameters (Bmax and KD).
Main Results:
- In crude synaptosomal fractions, GABA had no effect, but bicuculline and bicucine decreased binding affinity, an effect antagonized by GABA.
- In washed and processed membrane preparations, GABA increased binding affinity and, at higher concentrations, maximal binding capacity (Bmax).
- Endogenous GABA levels were estimated at approximately 3 X 10(-5) M in the crude synaptosomal fraction.
Conclusions:
- Endogenous GABA present in membrane preparations significantly influences 3H-diazepam binding assay outcomes.
- GABA and its antagonists, bicuculline and bicucine, appear to interact with the specific GABA binding site to modulate 3H-diazepam binding.