Pharmacological Effect of Turmeric on Cognitive Impairment Induced by Scopolamine in Mice

Abstract

Turmeric, a yellow spice, derived from the plant Curcuma longa has long been used in traditional diet and as an herbal medicine. It has profound pharmacological effect. Due to its neuroprotective action, it plays an active role in the treatment of various central nervous system disorders. The aim of the study was to evaluate the effect of turmeric on cognitive impairment in scopolamine treated mice. Scopolamine, a muscarinic antagonist, blocks cholinergic neurotransmission therefore impairing learning and memory. In this study, 1mg/Kg scopolamine was used to induce cognitive dysfunction in BALB/c mice. The effect of turmeric (20mg/Kg/day) on memory was investigated by various behavior tests like Morris water maze (MWM), social interaction test and exit circle test. Behavior analysis showed impairment in learning and memory in scopolamine treated mice. Following turmeric treatment, significant improvement was observed in scopolamine induced amnesic mice. In MWM escape latency on day 5th in case of scopolamine group (29.50 ± 2.836) was significantly high showing impaired learning and memory as compared to control (18.55 ± 3.908) and turmeric alone (16.48 ± 3.961) groups. Scopolamine + turmeric group (16.33 ± 2.522) showed significant (p < 0.01) decrease in latency time indicating that turmeric improved spatial learning. In social preference test, turmeric treatment in scopolamine amnesic group showed significant (p < 0.5) increase in sociability and social novelty as compared to scopolamine indicating positive effect of turmeric on social behavior. A significant (p < 0.001) improvement in the intrinsic inquisitiveness behavior was also observed in scopolamine + turmeric group relative to scopolamine group, once again showing turmeric’s positive effect. The study also includes evaluation of the effect of turmeric powder on the expression of Amyloid precursor protein (APP) isoforms (APP common, APP770, APP695) in hippocampus and cortex regions of brain. Turmeric decreased the expression of APP770 isoform that was amyloidogenic and improved the level of APP695 in hippocampus, and cortex. Difference in expression values was not significant. Therefore in the light of these findings turmeric may serve as a potential candidate in improving brain functions and cognitive properties. It can also act as a therapeutic option for psychiatric disorders including Alzheimer’s disease (AD)