Association between nicotine withdrawal and reward responsiveness in humans and rats.

IMPORTANCE Reward-related disturbances after withdrawal from nicotine are hypothesized to contribute to relapse to tobacco smoking but mechanisms underlying and linking such processes remain largely unknown. OBJECTIVE To determine whether withdrawal from nicotine affects reward responsiveness (ie, the propensity to modulate behavior as a function of prior reinforcement experience) across species using translational behavioral assessments in humans and rats. DESIGN, SETTING, PARTICIPANTS Experimental studies used analogous reward responsiveness tasks in both humans and rats to examine whether reward responsiveness varied in (1) an ad libitum smoking condition compared with a 24-hour acute nicotine abstinence condition in 31 human smokers with (n = 17) or without (n = 14) a history of depression; (2) rats 24 hours after withdrawal from chronic nicotine (n = 19) or saline (n = 20); and (3) rats following acute nicotine exposure after withdrawal from either chronic nicotine or saline administration. MAIN OUTCOMES AND MEASURES Performance on a reward responsiveness task under nicotine and nonnicotine conditions. RESULTS In both human smokers and nicotine-treated rats, reward responsiveness was significantly reduced after 24-hour withdrawal from nicotine (P < .05). In humans, withdrawal-induced deficits in reward responsiveness were greater in those with a history of depression. In rats previously exposed to chronic nicotine, acute nicotine reexposure long after withdrawal potentiated reward responsiveness (P < .05). CONCLUSIONS AND RELEVANCE These findings across species converge in suggesting that organisms have diminished ability to modulate behavior as a function of reward during withdrawal of nicotine. This blunting may contribute to relapse to tobacco smoking, particularly in depression-vulnerable individuals, to reinstate responsiveness to natural rewards and to experience potentiated nicotine-induced reward responsiveness. Moreover, demonstration of behavioral homology across humans and rodents provides a strong translational framework for the investigation and development of clinical treatments targeting reward responsiveness deficits during early withdrawal of nicotine.