Trait Impulsivity Predicts Escalation of Sucrose Seeking and Hypersensitivity to Sucrose-Associated Stimuli

Poor impulse control has been associated with compulsive drug seeking and an enhanced risk of relapse, suggesting that impulsivity is causally related to addiction proneness and relapse vulnerability. However, whether this association is specific to drugs of abuse or whether heightened impulsivity relates to a general increase in sensitivity to rewards and reward-associated stimuli is unknown. To address this issue, the authors selected rats on the basis of individual differences in impulsive action in the 5-choice serial reaction time task, after which they were subjected to an operant sucrose self-administration paradigm. High-impulsive rats displayed a progressive increase in responding on the active hole (including responses emitted during the time-out period) in comparison with low-impulsive rats, which reflects escalation of sucrose-seeking behavior. Once sucrose and sucrose-associated stimuli were omitted (extinction training), nose-poke responding ceased rapidly, an effect that was independent of impulsivity level. In contrast, on reintroduction of sucrose-associated stimuli, sucrose seeking was successfully reinstated in high-impulsive but not in low-impulsive rats. Collectively, the results suggest that impaired response inhibition is associated with enhanced responsiveness to reward-associated stimuli. As such, elevated impulsivity might constitute a risk factor for the initiation and maintenance of addictive behaviors.