Influence of nicotine and nitric oxide on anxiety behavior in mice

Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. Anxiety is considered to be a normal reaction to stress, however excessive anxiety results in anxiety disorder. In this study, we investigated the possible interaction between nicotine and nitric oxide system of the dorsal hippocampus on anxiety-like behavior in mice.

This experimental study was performed on 230 male NMRI mice. Mice were anesthetized with intra-peritoneal injection of ketamine hydrochloride, plus xylazine and then placed in a stereotaxic apparatus. Two stainless-steel cannulae were placed in the CA1 region of hippocampus. Nicotine (0.5 mg/kg) was injected intraperitoneally; L-arginine (1 µg/mouse) and L-NAME 50 ng/mouse was instilled in the cannulae; The elevated plus-maze test was used to test for anxiety-like behaviors. One-way analyses of variance (ANOVAs) followed by LSD test, were used for analysis of the data.

Intraperitoneal injection of nicotine or bilateral intra-dorsal hippocampal injections of L-arginine and L-NAME induced anxiogenic effects, p<0.05, p<0.05, p<0.01, respectively. Intraperitoneal injection of lower dose of nicotine (0.1 mg/kg) before different doses of L-arginine or L-NAME inhibited anxiogenic effects of L-arginine or L-NAME.

It seems that both nitric oxide and nicotinic cholinergic systems play a part in the modulation of anxiety in the dorsal hippocampus of mouse; however the interaction between these two systems is complex.