Chronic Administration of Bacopa monniera Alleviates Depressive Like Behavior and Increases the Expression of ERK1/2 in Hippocampus and Pre-Frontal Cortex of Chronic Unpredictable Stress Induced Rats

Abstract

Aims: Aim of the present study is to investigate the effect of Bacopa monniera in chronic unpredictable stress (CUS) induced depression in Sprague Dawley rats and its effect on ERK protein level. Study Design: Rats were subjected to CUS procedure and daily administration of BM intragastrically for consecutive 28 days. Place and Duration of Study: Department of Physiology, Raja Peary Mohan College, Uttarpara, Hooghly, West Bengal, India from February 2012-to July 2014. Methods: Various types of unpredictable stressors were applied for consecutive 28 days during CUS procedure including foot shock (1 mA, 1s duration, average 1 shock/min) for 60 min, 5 min cold water swim (at 4°C), 1 min tail pinch (1 cm from the end of the tail), 48 hour food deprivation, 24 hour water deprivation, and overnight illumination. The effect of BM treatment in CUS-induced depression was examined applying behavioral tests on rats including the sucrose consumption test that indicates anhedonia like behavioral change, open field test points out decreased locomotor activity which is indicative of a behavioral change that may reflect certain aspects of refractory depression and elevated plus maze test indicates decreased anxiety. We examined the possible mechanism of BM by measuring corticosterone level (ELISA), ERK1/2 and P-ERK1/2 level in rat hippocampus and prefrontal cortex (Western blot). Results: Four weeks of CUS exposure induced depression-like behavior in rats which is evidenced by significant decreases in sucrose consumption, decreased locomotor activity and short time spent in open arms (P=.05).In addition, it was found that corticosterone levels, ERK1/2, Phospho-ERK1/2 was significantly lower (P=.05) in CUS-treated rats. Daily administration of 80 mg/kg body weight of BM during the CUS interval significantly suppressed behavioral changes and reduced corticosterone levels, ERK1/2 and Phospho-ERK1/2 protein lev­els in the hippocampus and prefrontal cortex. Conclusion: The present study advocates that BM can attenuate depression and also confirms that 80 mg/kg doses of BM extract have significantly higher antidepressant-like activity.