?-Aminobutyric Acid: Temperature Dependence in Benzodiazepine Receptor Binding

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Abstract
The effects of muscimol and/or incubation temperature on the inhibition of [3H]flunitrazepam receptor binding by benzodiazepine receptor ligands were investigated. At 0°C muscimol decreased the Ki values for some ligands as displacers of [3H]flunitrazepam binding to brain-specific sites while increasing or having no effect on the Ki values for other ligands. The Ki values for some ligands are higher at 37°C than at 0°C but are reduced by muscimol at both 0° and 37°C. In contrast, the ligands whose Kt values are increased by muscimol either decreased or did not alter the Ki values at 37°C as compared to those at 0°C. Incubation of membranes at 37°C for 30 min accelerated γ-aminobutyric acid (GABA) release by 221% over that at 0°C. These results indicate that changes in incubation temperature alter benzodiazepine receptor affinity for ligands via GABA.