Non-deprived male rats were familiarized with a highly palatable diet until baseline consumption in a 30-min daily access period had stabilised. Stereospecificity of the hyperphagic effect of
benzodiazepine receptor agonists was demonstrated using two enantiomers, the (S)-enantiomer being
Ro11-3128 (methylclonazepam) and the (R)-enantiomer,
Ro11-3624. The
benzodiazepine receptor antagonists, Ro15-1788 and
CGS 8216, reversed the hyperphagic effect of
Ro11-3128. These data confirm the mediation of the hyperphagic effect of
benzodiazepines by specific receptors. In further experiments, the effects of the pyrazoloquinolines
CGS 9895 and
CGS 9896 were examined both alone and also in combination with
clonazepam. In doses of 1.25-10.0 mg/kg, neither
CGS 9895 nor
CGS 9896, when given alone, had a significant effect on the consumption of the palatable diet. Both, however, dose-dependently antagonised the hyperphagic effect of
clonazepam. In a test of palatable food consumption, therefore, both compounds can be characterised as
benzodiazepine antagonists.