Nicotine withdrawal symptoms comprise insomnia, depression, anxiety, attention disorders, and increased craving. We evaluated the ameliorating effect of treadmill exercise on nicotine withdrawal symptoms. The rats in the nicotine withdrawal groups received subcutaneous injection with 6-mg/kg nicotine hydrogen tartrate salt for 17 days. And then, the injection of nicotine hydrogen tartrate salt was stopped next for 2 weeks. The rats in the exercise groups performed treadmill running once a day, 5 days per week, for 31 days. In the present results, activity was decreased and anxiety-like behavior was observed in the nicotine withdrawal rats. Treadmill running increased activity and ameliorated anxiety-like behavior in the nicotine-withdrawal rats. Expressions of tryptophan hydroxylase (TPH) and 5-hydroxytryptamine (5-HT) in the dorsal raphe were decreased in the nicotine withdrawal rats, in contrast, treadmill running increased TPH and 5-HT expressions. Impaired short-term memory and deteriorated spatial learning ability were observed in the nicotine withdrawal rats, in contrast, treadmill running ameliorated impairment of short-term memory and spatial learning ability. Expressions of brain-derived neurotrophic factor and tyrosine kinase B (TrkB) were decreased in the nicotine withdrawal rats, in contrast, treadmill running increased brain-derived neurotrophic factor and TrkB expressions. The numbers of the doublecortin (DCX)-positive cells and 5-bromo-2'-deoxyuridine (BrdU)-positive cells in the dentate gyrus were suppressed in the nicotine withdrawal rats, in contrast, treadmill running enhanced the numbers of DCX-positive cells and BrdU-positive cells. The present study demonstrate that treadmill exercise ameliorated nicotine withdrawal-induced anxiety, depression, and memory impairment.
Keywords: Anxiety; Depression; Neurogenesis; Nicotine; Treadmill exercise.