Wheel running exercise attenuates vulnerability to self-administer nicotine in rats

Background: Preventing or postponing tobacco use initiation could greatly reduce the number of tobacco-related deaths. While evidence suggests that exercise is a promising treatment for tobacco addiction, it is not clear whether exercise could prevent initial vulnerability to tobacco use. Thus, using an animal model, we examined whether exercise attenuates vulnerability to the use and reinforcing effects of nicotine, the primary addictive chemical in tobacco. Methods: Initial vulnerability was assessed using an acquisition procedure wherein exercising (unlocked running wheel, n = 10) and sedentary (locked or no wheel, n = 12) male adolescent rats had access to nicotine infusions (0.01-mg/kg) during daily 21.5-h sessions beginning on postnatal day 30. Exercise/sedentary sessions (2-h/day) were conducted prior to each of the acquisition sessions. The effects of exercise on nicotine's reinforcing effects were further assessed in separate groups of exercising (unlocked wheel, n = 7) and sedentary (no wheel, n = 5) rats responding for nicotine under a progressive-ratio schedule with exercise/sedentary sessions (2-h/day) conducted before the daily progressive-ratio sessions. Results: While high rates of acquisition of nicotine self-administration were observed among both groups of sedentary controls, acquisition was robustly attenuated in the exercise group with only 20% of exercising rats meeting the acquisition criterion within the 16-day testing period as compared to 67% of the sedentary controls. Exercise also decreased progressive-ratio responding for nicotine as compared to baseline and to sedentary controls. Conclusions: Exercise may effectively prevent the initiation of nicotine use in adolescents by reducing the reinforcing effects of nicotine. (C) 2015 Elsevier Ireland Ltd. All rights reserved.