Absence of Intrinsic Antagonist Actions of Benzodiazepine Antagonists on an Exploratory Model of Anxiety in the Mouse

Recent reports suggest that antagonists of benzodiazepine receptors have intrinsic anxiogenic and convulsant properties. An exploratory model in the mouse, specific for anxiolytics, was employed to test further, the hypothesis that antagonists have intrinsic actions pharmacologically opposite to those of the benzodiazepines. The drugs Ro 15-1788 (ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H- imidiazo -[1,5-a] [1,4]benzodiazepine-3-carboxylate), CGS-8216 (2-phenylpyrazolo[4,3-c] quinolin -3[5H]one), beta-CCM (3-carbomethoxy-beta-carboline) and FG-7142 (N1-methyl-beta-carboline-3-carboxamide) all effectively blocked the anxiolytic actions of diazepam. None of these antagonists demonstrated intrinsic or anxiogenic or anxiolytic activity in this model system. These findings suggest that both the species and paradigm employed will determine the pharmacological profile of drugs which act at the GABA-benzodiazepine receptor complex.