Effect of Turmeric on Learning and Memory in Stress and Scopolamine Induced Amnesia

Abstract

Brain is the key organ of central nervous system. Cholinergic system is involved in higher cognitive functions like learning and memory. The most important brain regions of the brain involved in learning and memory are the prefrontal cortex and the hippocampus. Various factors are known to impair memory. Chronic stress is also involved in memory impairment by activating Hypothalamic-Pituitary Axis, which in turns activates release of corticosterone in the blood. Cholinergic system blockade by muscarinic antagonist like scopolamine also impairs memory. Turmeric is a traditional herb used in daily diet in South Asia and has potential to improve memory. In this study, effect of stress on cortex and hippocampus dependent memory was explored by using different behavior tests. Effect of turmeric (20mg/kg) on expression of muscarinic genes in stress induced animals was also investigated. On the other hand, expression of muscarinic genes and the severity in the memory impairment due to stress and cholinergic blockade was also investigated. Increased corticosterone levels were observed in stressed animals when compared to control, while turmeric treatment significantly reduced (P < 0.0001) corticosterone levels in blood. Turmeric treatment resulted in improved (p < 0.0001) learning and memory in stressed animals as compared to those which were not treated with turmeric. Social novelty preference was also restored (p<0.01) in turmeric treated animals. Following turmeric treatment, expression of muscarinic receptor gene M1, M3 and M5 were significantly improved (p < 0.05) as compared to stress induced and stress + scopolamine induced animals. Stress group and stress + scopolamine group showed almost same expression of down regulation muscarinic gene. These findings highlight the role of turmeric in cognitive functions and memory, thus presenting it as an effective candidate for treatment of amnesia.