The study of Rodd et al. (2008) examined the effects of operant responding for a 0.0125% saccharin solution (approximately 500 lever presses/session for 10 weeks) and did not observe any significant effects on gene expression in the Acb of inbred P rats, suggesting that instrument responding per se is not producing alterations in gene expression. The results of the current study are consistent with the observed effects being due to repeated excessive binge-like alcohol drinking, and not mainly a result of instrument responding.
