Antagonism of the discriminative effects of diazepam by pyrazoloquinolines in rats.

The diazepam-like agonist and diazepam antagonist properties of the pyrazoloquinoline benzodiazepine receptor ligands CGS8216, CGS9895 and CGS9896 were evaluated in rats trained to discriminate between saline and 1.0 mg/kg of diazepam in a two-choice, discrete-trial procedure. None of the three pyrazoloquinolines produced diazepam-like discriminative effects over the dose range of 1.0-30 mg/kg. The effects of 1.0 mg/kg of diazepam were antagonized by CGS8216 and CGS9895, but not by CGS9896. The present results provide behavioral evidence for benzodiazepine receptor heterogeneity.