Effects of longan seed extract on scopolamine-induced learning and memory deficit in mice

Abstract

Longan (Euphoria longana) seed is a traditional Chinese medicinal plant which has been claimed to have positive effect on deficit in learning and memory. In this study, the effects of crude ethanolic extracts of longan seed on learning and memory impairment induced by scopolamine were investigated in mice. With reference to saline-treated group, scopolamine-treated mice demonstrated impairment of learning and memory seen as an increment of the latency to find the platform in learning trial in Morris water maze as well as a reduction of latency and an increased numbers of error in step-down test. Performances of mice receiving longan seed extract at the dose of 300 mg/kg once daily were not different from those of the scopolaminetreated group. However, oral administrations of longan seed extract at the dose of 1,000 mg/kg significantly reduced the latency to find the platform in Morris water maze test but showed no improvement on the passive avoidance task. Additionally, injection of scopolamine depressed locomotor activity which were unaffected by the administration of longan seed extract. Furthermore, we had investigated the effect of longan seed extract on brain lipid peroxidation in scopolamine-treated mice and found that the administration of neither scopolamine nor longan seed extract exerted effect on malondialdehyde level of the brain. In conclusion, the present study has demonstrated the beneficial effects of longan seed extract for learning and memory deficit induced by scopolamine. Further investigation is needed to explore whether longan seed extract could be beneficial for memory impairment in Alzheimer's disease in which cholinergic deficit is one of the hallmarks.