Acute, stress-induced changes in the benzodiazepine/gamma-aminobutyric acid receptor complex are confined to the chloride ionophore.

Rapid and robust changes in the chloride ionophore component of the benzodiazepine/gamma-aminobutyric acid receptor complex ("supramolecular complex") were observed in the central nervous system of rats exposed to a brief, ambient temperature swim stress. Stress-induced modification of the chloride ionophore was manifest as an increase in the efficacy of halides (Cl-, Br- and I-) to enhance [3H]flunitrazepam binding. In contrast, neither gamma-aminobutyric acid-enhanced [3H]flunitrazepam binding nor [3H] flunitrazepam binding assayed in the absence of halide ions was altered by stress. Furthermore, the number of [35S]t-butylbicyclophosphorothionate binding sites and the apparent affinity of this radioligand were increased as a result of stress, as was the ability of Cl- and low concentrations of muscimol to increase the binding of this radioligand. These changes could represent the physiological attempt of an organism to compensate for stressful changes in the environment.