The effect of benzodiazepine and beta-carboline inverse agonists on body temperature in mice was investigated using doses shown to be pro-convulsant in other studies. The benzodiazepine partial inverse agonists Ro 15-3505 (0.1-30 mg/kg i.p.), Ro 15-4513 (0.1-10 mg/kg i.p.) and the fuller benzodiazepine inverse agonist Ro 19-4603 (0.03-0.3 mg/kg i.p.) had no effect on rectal temperature. Ro 19-4603 (1 mg/kg i.p.) produced a small hypothermic response. In contrast, the beta-carboline partial and full inverse agonists, FG 7142 (30, 60 mg/kg i.p.) and methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (3, 10 mg/kg i.p.), produced large decreases in body temperature. These differential effects of benzodiazepine and beta-carboline inverse agonists on body temperature may provide further evidence for the existence of benzodiazepine receptor subtypes.
