Anticonvulsant activity of Nymphaea lotus Linn. extract in mice: The role of GABAergic-glutamatergic neurotransmission and antioxidant defence mechanisms

Abstract

Epilepsy remains an unmet medical need affecting more than 50 million people worldwide with about 125,000 mortality annually and more prevalent in low- and middle-income countries. Nymphaea lotus (also known as water lilly) is an aquatic plant used traditionally to treat convulsive episodes in Southwestern Nigeria. This study was undertaken to evaluate anticonvulsant activity of aqueous Nymphaea lotus extract (ANL) and ethanol Nymphaea lotus extract (ENL) on chemical-induced seizures in mice as well as possible mechanisms of action. Vehicle (10 mL/kg, p.o.), ANL (50–200 mg/kg, p.o.), ENL (50–200 mg/kg) or diazepam (5 mg/kg, p.o.) was administered 1 h prior to chemo-convulsant (picrotoxin (PCT), pentylenetetrazol (PTZ), strychnine or N-methyl-D-aspartate (NMDA)) administration. Most effective doses of the extracts were administered to mice after the establishment of temporal lobe epilepsy (TLE) induced by kainic acid. Thereafter, memory assessment in Y-maze, depressive-like behaviour in tail suspension test (TST) and anxiety model in elevated plus maze test (EPM). The prefrontal cortex and hippocampus were assayed for oxidative stress parameters. The pretreatment of mice with ANL or ENL significantly prolonged onset of seizures and reduced the duration of picrotoxin-, pentylenetetrazol-, and strychnine-induced seizures or NMDA-induced turning behaviour. Kainic acid induced spontaneous recurrent seizures and oxidative stress were ameliorated by N. lotus extracts. Moreover, N. lotus-induced anticonvulsant action was reversed by the pretreatment of mice with flumazenil (benzodiazepine receptor antagonist) or L-arginine (nitric oxide precursor). In addition, kainic acid induced neurodegeneration was reduced by N. lotus extract. Findings from this study showed anticonvulsant activity of Nymphaea lotus in neurotoxins-induced seizures through enhancement of inhibitory GABAergic/ antioxidant signalling and inhibition of glutamatergic neurotransmission