Behavioral and Biochemical Interaction Between Nicotine and Chronic Unpredictable Mild Stress in Mice.

Nicotine, the main component of tobacco smoke, exerts influence on mood, and contributes to physical and psychological dependence. Taking into account frequent concomitance of nicotine abuse and stress, we aimed to research behavioral and biochemical effects associated with nicotine administration in combination with chronic unpredictable mild stress (CUMS). Mice were submitted to the procedure of CUMS for 4 weeks, 2 h per day. Our results revealed that CUMS-exposed animals exhibited behavioral alteration like anxiety disorders in the elevated plus maze (EPM) test, the disturbances in memory in the passive avoidance (PA) test and depressive effects in the forced swim test (FST). Moreover, nicotine (0.05-0.5 mg/kg), after an acute or subchronic administration decreased stress-induced depression- and anxiety-like effect as well as memory deficit. Administration of metyrapone (50 mg/kg), a glucocorticosteroid antagonist, alleviated the depressive effect induced by the CUMS. The biochemical experiments showed decreased values of the total antioxidant status (TAS), activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) with simultaneously increased in malondialdehyde (MDA) concentration in mice submitted to the CUMS. The same effects were observed after an acute and subchronic nicotine administration within all examined brain structures (i.e., hippocampus, cortex, and cerebellum) and in the whole brain in non-stressed and stressed mice confirming pro-oxidative effect of nicotine. Our study contributes to the understanding of behavioral and biochemical mechanisms involved in stress-induced disorders such as depression, anxiety and memory disturbances as well as dual nicotine-stress interactions on the basis of the development of nicotine dependence.