Chronic Administration of <i> Curcuma longa </i>Extract Improves Spatial Memory-Related Learning Ability in Aged Rats by Inhibiting Brain Cortico-Hippocampal Oxidative Stress and TNF<i>α</i>

We studied on the effect of Curcuma longa extract on spatial learning-related memory ability of old rats in eight-arm radial maze task. Rats were randomly divided into two groups: one group was orally administered 100 mg/KgBW/day C. longa extract (CLE) dissolved in deionized water and the other group was administered the vehicle alone for 10 weeks. The rats were tested with the partially baited eight-arm radial maze to evaluate two types of spatial memory-related learning ability displayed by reference memory errors (RMEs) and working memory errors (WMEs). Chronic administration of CLE significantly decreased the number of RMEs and WMEs, concurrently with the decreases in the cortico-hippocampal levels of lipid peroxides (LPO) and tumor necrosis factor alpha (TNF-α). In a parallel set of experiments, CLE-pretreated rats of the same age group were subjected to hypoxia-reperfusion injury by carotid artery occlusion to induce oxidative stress in the brains in order to examine whether such an in vivo hypoxia-induced oxidative stress could be ameliorated by the extract. Again, the levels of LPO were significantly decreased in the cortico-hippocampal tissues of the CLE-fed hypoxic rats. The histology of the brains also revealed that the CLE-pretreated rats had retained improved cellular integrity. Finally, our results provide the evidence that oral administration of C. longa extract increases the defense against oxidative stress and proinflammatory TNF-α, concurrently with the improvement of memory-related brain cognitive ability of the aged rats.