Abstract

Background and purpose Evidence suggests that exercise decreases nicotine withdrawal symptoms in humans; however, the mechanisms mediating this effect are unclear. We investigate, in a mouse model, the effect of exercise intensity during chronic nicotine exposure on nicotine withdrawal severity, binding of α4β2*, α7 nicotinic acetylcholine (nAChR), μ-opioid (μ receptors) and D2 dopamine receptors, and on brain-derived neurotrophic factor (BDNF) and plasma corticosterone levels. Experimental approach Male C57Bl/6J mice treated with nicotine (minipump, 24 mg kg-1 day-1) or saline for 14 days underwent one of three concurrent exercise regimes: 24, 2 or 0 hrs day-1 voluntary wheel running. Mecamylamine-precipitated withdrawal symptoms were assessed on day 14. Quantitative autoradiography of α4β2*, α7 nAChRs, μ receptors and D2 receptor binding was performed in brain sections of these mice. Plasma corticosterone and brain BDNF levels were also measured. Key results Nicotine-treated mice undertaking 2 or 24 hrs day-1 wheel running displayed a significant reduction of withdrawal symptom severity compared with the sedentary group. Wheel-running induced a significant upregulation of α7 nAChR binding in the CA2/3 area of the hippocampus of nicotine-treated mice. Neither exercise nor nicotine treatment affected μ or D2 receptor binding or BDNF levels. Nicotine withdrawal increased plasma corticosterone levels and α4β2* nAChR binding, irrespective of exercise regimen. Conclusions and implications We demonstrate for the first time a profound effect of exercise on α7 nAChRs of nicotine-dependent animals, irrespective of exercise intensity. These findings shed light onto the mechanism underlining the protective effect of exercise in the development of nicotine dependence.