NEUROPHARMACOLOGICAL EVALUATION OF ETHANOLIC LEAF EXTRACT OF ALTERNANTHERA BRASILIANA (L.) KUNTZE (AMARANTHACEAE) IN MICE

Alternanthera brasiliana is a medicinal plant used in the folkloric treatment of malaria, pains, infections and diabetes in South-western states of Nigeria. Recent reports indicate some central activities for the plant. This study evaluated ethanolic leaf extract of the plant for novelty-induced behaviour, anxiety, sedation and convulsion in mice. Dried powdered leaves of the plant were extracted with 70% ethanol, filtered and   concentrated in vacuo to obtain ethanolic leaf extract (ELE) of A. brasiliana. The acute toxicity (LD₅₀) of the ELE was determined through oral (p.o.) and intraperitoneal (i.p.) routes. ELE (250, 500 and 1000 mg/kg, p.o.) was evaluated for novelty induced behaviours, anxiolytic, sedative and anticonvulsant activities. The LD₅₀ values obtained for the ELE were ≥5000 mg/kg, p.o. and 3808 mg/kg, i.p.  The ELE (500-1000 mg/kg) caused significant (p<0.05) increase in rearing [p<0.05, p< 0.01; F_{(4, 25)}= 37.0] and locomotor [p<0.05, p< 0.01; F_{(4, 25)}= 36.0] activities; caused increase in the number of head dips at 1000 mg/kg [p<0.01, F_{(4, 25)} = 9.0] and non-significantly increased time spent on the open arms of the elevated plus maze; caused significant increase in sleep latency [p<0.01, F_{(4, 25)}=37.0] but decrease non-significantly total sleeping time induced by ketamine. Finally, the ELE at all the doses used did not protect the animals against PTZ, strychnine or incidence of tonic hind limb extension on MES. This study concluded that ethanolic leaf extract of A. brasiliana on the central nervous system is stimulatory; possess moderate anxiolytic activity but lack anticonvulsant activity