Comparative effects of Rauwolfia vomitoria and chlorpromazine on social behaviour and pain

Background: Rauwolfia vomitoria has been used in Nigeria to manage psychiatric disorders despite orthodox medicine. Aims: This research was therefore aimed at comparing the effects of R. vomitoria, chlorpromazine and reserpine on social behaviour and pain in mice. Materials and Methods: Ninety male CD-1 mice (32 – 38g body weight) were grouped into 3 with 5 subgroups (n=6) each. Mice were given chlorpromazine (0.0, 0.25, 1.0, 2.0, 4.0 mg/kg i.p.), 30 minutes before testing and R. vomitoria (0.0, 0.25, 1.0, 2.0, 4.0 mg/kg, i.p.) and reserpine (0.0, 0.1, 0.4, 0.8, 1.6 mg/kg, i.p) 24 hours before testing. Nesting score assessed social behaviour while the tail flick and hot plate analgesiometers assessed pain. Results: Chlorpromazine dose-dependently decreased nesting score (F4,25 = 5.5660; p< 0.01), indicating decreased social behaviour (social loss) in the mice. Although R. vomitoria did not affect nesting score, reserpine decreased the nesting score (social loss). In the pain test, chlorpromazine did not alter tail flick latency but decreased hind paw lick latency in the hot plate at 2.0 and 4.0 mg/kg (p< 0.01), indicating increased pain sensitivity at these doses which may indirectly increase social withdrawal and thus aggravating depression. R. vomitoria however, increased tail flick and hind paw lick latencies in the hot plate test (p< 0.05) indicating decreased pain sensitivity. Reserpine, like R. vomitoria, increased latency of hind paw lick in the hot plate. Conclusion: R. vomitoria has a high potential as an antipsychotic and may have advantage over chlorpromazine; it is not necessary to isolate active components from this herb.