Investigating cumulative effect of curcumin and vitamin d on learning and memory using restraint stress mice model

Abstract

Background: Chronic stress causes memory impairment. Curcumin, main secondary metabolite of Curcuma longa, has limited applications as a neuroprotectant due to its low bioavailability. Vitamin D, a fat-soluble secosteroid, has independently shown to improve cognitive functions. Objective: To examine the synergistic effect of curcumin and vitamin D on memory impairment caused by restrained stress. Methods: Restraint stress was induced in BALB/c mice. 30 mg/kg of curcumin and/or 1500 IU of vitamin D were administered orally. Learning and memory were evaluated by behavior tests; novel object recognition, and Morris water maze (MWM) test. Results: Percentage recognition index which is a measure of animal’s ability to discriminate between a familiar object and novel object, was decreased in stress group (39.4±6.95) as compared to control (60.7±3.37). An improvement in exploratory behavior and recognition memory was seen in stressed mice following treatment with curcumin and/or vitamin D (stress + curcumin = stress + curcumin + vitamin D). For spatial memory, decreasing trend in escape latencies was observed for all, with stress group performing equally well, indicating that restrained stress might not cause a notable impairment of spatial memory. On the other hand, reference memory, assessed from probe trial was significantly impaired in stress group (10.33±1.33). Following treatment with curcumin alone (31.33±2.02) or in combination with vitamin D (29.33±5.2) a significant improvement was seen in stressed mice; however, a cumulative effect was not observed. Conclusion: Restraint stress model showed significant decline in cognitive functions. Treatment with curcumin alone and in combination with vitamin D counteracted stress and improved learning and memory, although a significant cumulative effect was not seen. Further studies with focus on the molecular aspects of learning and memory are needed.