Cue-induced nicotine-seeking behavior after withdrawal with or without extinction in rats.

Exposure to smoking-associated environmental cues during smoke cessation elicits self-reported urge/craving to smoke, which precipitates relapse even after prolonged abstinence. Incubation of cue-induced cigarettes craving during abstinence has been observed in human smokers recently. The present studies assessed cue-induced nicotine-seeking behavior under different withdrawal conditions in rats with a history of nicotine self-administration. We found that non-reinforced operant responding during cue-induced nicotine seeking after different periods of withdrawal from nicotine exhibited an inverted U-shaped curve, with higher levels of responding after 7-21 days of withdrawal than those after 1-day withdrawal. Cue-induced nicotine-seeking responding is long lasting and persists even after 42 days of forced withdrawal in the home cages. Interestingly, repeated testing of cue-induced nicotine seeking at different withdrawal time points (1, 7, 14, 21 and 42 days) in the same individual alleviated responding as compared with the between-subjects assessment. Furthermore, extinction training during nicotine withdrawal significantly decreased cue-induced reinstatement of nicotine-seeking behavior. Together, profound time-dependent incubation of cue-induced craving in nicotine-experienced rats were observed. In addition, repeated cue exposure or extinction training decreases cue-induced craving. The demonstration of incubation of nicotine craving phenomenon in both rat and human studies provides support for the translational potential of therapeutic targets for relapse uncovered through mechanism studies in rats.