Modulation of nitrergic signalling pathway by American ginseng attenuates chronic unpredictable stress-induced cognitive impairment, neuroinflammation, and biochemical alterations

Prolonged stress causes extensive loss of neurons leading to deficits in cognitive performance. Increasing evidence indicates that accumulation of intercellular messenger, nitric oxide (NO), plays a crucial role in the pathogenesis of memory disorders. American ginseng (AG) is known to show protection in different animal models of neurological diseases; however, its exact mechanism of action is not clearly understood. Therefore, the current study was designed to investigate the interaction of AG against chronic unpredictable stress (CUS)-associated behavioral and biochemical alterations and the probable role of nitrergic pathway in this effect. Male Laca mice were exposed to a series of stressors along with drug/vehicle treatment daily for 28 days. CUS paradigm caused significant impairment in both acquisition and retention memory as measured in Morris water maze and elevated plus maze task. This was coupled with alterations in oxidative stress markers, mitochondrial enzyme complex activities, pro-inflammatory cytokine (TNF-alpha), and acetylcholinesterase levels in the hippocampus as compared with na < ve group. Besides, there was a marked increase in serum corticosterone levels. AG (100, 200 mg/kg; p.o.) treatment significantly improved cognitive impairment; reduced TNF-alpha, acetylcholinesterase, and corticosterone levels; and attenuated oxidative-nitrergic stress. Furthermore, pre-treatment of l-arginine (100 mg/kg; i.p.), a nitric oxide donor, with subeffective dose of AG (100 mg/kg; p.o.) reversed its protective effects. However, l-NAME (10 mg/kg, i.p.), a non-specific NO synthase inhibitor, potentiated the effects of AG. Our findings suggest that modulation of nitrergic signalling cascade is involved in the protective effects of AG against CUS-induced cognitive dysfunction, oxidative stress, and neuroinflammation.