RESUMEN
Aims: This study evaluated the anxiolytic, sedative and hypothermic effects of aqueous leaf extract of Vernonia amygdalina in Mice. Study Design: One-factor two control groups experimental design. Place and Duration of Study: Department of Pharmacology, Faculty of Pharmacy, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria, between October 2012 and January 2013. Methodology: Animal models of novelty induced behaviours (rearing and locomotion), anxiolysis (T-maze and hole-board), sedation (amylobarbitone induced hypnosis) and hypothermia (rectal temperature measurement) were utilized in this study. Five different groups of white albino mice of both sexes weighing 23 – 28g (n=5 or 6) were randomly selected. Group 1 was the control (normal saline, 10 ml/kg, i.p.), group 2 was the positive control (diazepam, 1mg/kg, i.p.), while group 3, 4 and 5 were treated with aqueous leaf extract at 50, 100 and 200mg/kg, i.p., respectively. All animals in each group were pretreated for 30 minutes before assessment. Results: V. amygdalina at 50 mg/kg showed anxiolytic activity by significantly (P<0.001) increasing the frequency of head-dip compared to control, and also a significant (P =.05) decrease and increase (P<0.001) in latencies to withdrawal from the closed and open arms of the elevated T-maze respectively. However, at 100-200mg/kg, V. amygdalina showed sedative activity by significantly (P<0.001) decreasing rearing, locomotion (P<0.001) and head-dip frequency (P<0.001) in mice. Furthermore, V. amygdalina (100- 200mg/kg) caused significant (P<0.001) decrease in sleep latency and significantly (P<0.001) increased sleep duration in amylobarbitone-induced sleeping test indicating sedative activity. V. amygdalina (50-200mg/kg) also caused significant (at 30 min, 60 min, 90 min and 120 min; P=.05) reduction in rectal temperature in mice compared to normal saline and diazepam. Conclusion: The aqueous leaf extract of V. amygdalina may possess anxiolytic, sedative and hypothermic effects, hence justifying its folkloric medicinal use.