Effects of turmeric extract (Curcuma longa) on impairment of learning and memory induced by either cerebral ischemia or scopolamine in mice

Abstract

The effects of turmeric extract (Curcuma longa) on learning and memory impairment induced by transient cerebral ischemia (bilateral occlusion of common carotid arteries, 2VO) was investigated in mice. The 2VO caused an impairment of learning and memory seen as an increase in the latency to find the platform in Morris Water Maze (MWM) test as well as a reduction of step-down latency and an increment of number of errors in step-down test. Administration of turmeric extract (p.o.) at doses of 100, 300 and 1000 mg/kg/day significantly reduced the latency to find the platform of 2VO mice in MWM test. Furthermore, in passive avoidance task, turmeric extract at doses of 300 and 1000 mg/kg/day were found to increase the step-down latency and decrease the number of error of 2VO mice. Similar results were observed in learning and memory deficit induced by scopolamine. In addition, it was found that injection of scopolamine but not 2VO significantly depressed locomotor activity and none of the observed effects was affected by the administration of turmeric extract. Based on the results that turmeric extract could antagonize amnesic effect of scopolamine, it is suggestive that turmeric extract might exert its memory enhancing effect through a correction of cholinergic deficit. Moreover, turmeric extract could suppress 2VO-induced increasing of brain malondialdehyde. Thus it is likely that memory enhancing effect of turmeric extract might be accounted by its antioxidative effect. In conclusion, the present study has demonstrated the beneficial effects of turmeric extract for learning and memory deficit induced by cerebral ischemia and scopolamine. It is possible that antioxidant property of turmeric extract and its effect on cholinergic system could, at least partly, contribute to its positive effect on memory deficit in 2VO and scopolamine model. Thus, turmeric extract might be beneficial for memory impairment in Alzheimers disease which oxidative stress and cholinergic system are underlying cause.