Evaluation of the analgesic effect of aqueous extract of Brugmansia suaveolens flower in mice: possible mechanism involved.

The study was conducted to test the aqueous extract of Brugmansia suaveolens (AEBs) flowers for their antinociceptive effects in mice. In the hot plate test, a significant increase in reaction time for two doses of AEBs at 60, 90, 120, and 150 min after treatment was noted. Pretreatment of animals with naloxone (5 mg/kg, intraperitoneally [IP]) left the antinociceptive effect of AEBs at a dose of 100 mg/kg unaffected at 60, 90, 120, and 150 min after treatment and at a dose of 300 mg/kg at 30 min but not at 90, 120, and 150 min. In the writhing test, the AEBs significantly inhibited acetic acid-induced abdominal constriction and was equally potent at both doses. Pretreatment with naloxone (5 mg/kg, IP) left the antinociceptive effect of both doses of AEBs unaffected. Pretreatment with N(G)-nitro-L-arginine methyl ester (L-NAME; 20 mg/kg, IP) caused a significant change in the number of abdominal constrictions but did not change the antinociceptive effect of AEBs. Pretreatment of animals with methylene blue also did not change the effect of AEBs on the number of writhing movements in mice. Flumazenil (5 mg/kg, IP) antagonized the antinociceptive effects of diazepam and also reversed the antinociceptive effect of AEBs. AEBs showed a depressant effect on the central nervous system, and the treatment of mice with pentobarbital combined with AEBs increased the animals' sleeping time in a dose-dependent manner. These results suggest that the antinociceptive activity of AEBs may be related in part to benzodiazepine receptors, although peripheral mechanisms cannot be excluded.