Binge-like intake of sucrose reduces the rewarding value of sucrose in adult rats

Binge eating disorder is the most common eating disorder, but its underlying etiology is poorly understood. Both humans and animals exhibit binge-like intake of highly-palatable food, suggesting that the behavior is driven by the rewarding properties of food, rather than homeostatic signals. Food reward is regulated, in part, by endogenous opioid mechanisms which, themselves, may be altered by excessive eating. We examined this hypothesis by testing whether binge-like sucrose intake modifies the subsequent development of a conditioned place preference (CPP) to sucrose and morphine in both female and male adult rats. Separate groups were given intermittent (12h) or continuous (24 h) access to a sweet solution (10% sucrose or 0.1% saccharin) and food in their home cage over 28 days. Intermittent sucrose access induced binge-like intake, defined as increased consumption within the first hour; importantly, daily sucrose intake was similar for continuous and intermittent access groups. In a later test, all rats developed a conditioned place preference (CPP) to 15% sucrose with the exception of female and male rats given 12-h intermittent access to sucrose. In a separate experiment, all groups displayed a CPP to morphine (4 mg/kg). These findings demonstrate that binge-like sucrose intake, not just increased consumption, disrupts reward processing without affecting stimulus-reward learning. This fits with clinical evidence of hypo-reward responsivity in patients with binge eating disorder.