Effects of curcumin on learning and memory deficits, BDNF, and ERK protein expression in rats exposed to chronic unpredictable stress.

Accumulating evidence suggests that cognitive processes, such as learning and memory, are affected in depression and antidepressant treatment may ameliorate cognitive impairments. Recent studies have shown that curcumin exhibits antidepressant-like effects. The aim of the present study was to determine whether curcumin administration influences chronic unpredictable stress (CUS)-induced cognitive deficits and explores underlying mechanisms. Male Wistar rats were subjected to CUS protocol for a period of 5 weeks to induce depression. The depressive-like behavior was tested using sucrose preference test, open field test and Morris water maze test. Effects of curcumin on brain-derived neurotrophic factor (BDNF) and extracellular signal-regulated kinase (ERK) levels in the hippocampus were also examined. Chronic treatment with curcumin significantly reversed the CUS-induced behavioral and cognitive parameters (reduced sucrose preference and impaired learning and memory function) in stressed rats. Additionally, CUS reduced hippocampal BDNF and ERK levels, while curcumin effectively reversed these alterations. Taken together, our results indicate that the antidepressant-like effects of curcumin in CUS rats are related to its aptitude to promote BDNF and ERK in the hippocampus.