FLUMAZENIL DOES NOT ANTAGONIZE HALOTHANE, THIAMYLAL OR PROPOFOL ANAESTHESIA IN RATS{dagger}

We have studied the effects of flumazenil on sleep time andEEG in rats anaesthetized with 1.5% halothane, propofoi 20 mgkg^–1, thiamylal 30 mg kg^–1, or combinations of diazepam5 mg kg^–1 and anaesthetic agents. We also studied theeffects of flumazenil 0.3, 3 and 30 mg kg^–1 on behaviourand EEG. Flumazenil 0.3 and 3 mg kg^–1 alone had no effecton behaviour or EEG, but flumazenil 30 mg kg^–1 had depressiveeffects similar to those of diazepam on behaviour and EEG. Flumazenil0.3, 3 and 30 mg kg^–1 i.v., antagonized the effects ofdiazepam 10 mg kg^–1 i.v. on behaviour and EEG. Flumazenilhad no antagonistic effect on sleep time induced by anaestheticagents, but flumazenil 30 mg kg^–1 potentiated propofol-inducedanaesthesia. Flumazenil did not affect anaesthesia-induced EEGchanges. Diazepam 5 mg kg^–1 potentiated anaesthesia. Flumazenilantagonism of diazepam potentiation varied with anaestheticagent: flumazenil 0.3 mg kg^–1 antagonized diazepam actionin halothane anaesthesia, but 30 mg kg^–1 was requiredin propofoi anaesthesia; this large dose was insufficient inthiamylal anaesthesia. ^*Present address: Department of Anesthesia, Omiya Medical Center,Omiya 330, Japan.