Protracted motivational dopamine-related deficits following adolescence sugar overconsumption

Adolescence represents a critical period characterized by major neurobiological changes. Chronic stimulation of the reward system during adolescence might constitute an important factor of vulnerability to pathological development. Increasing evidences suggest that adolescent overconsumption of sweet palatable foods impact reward-based processes. However, the neurobiological bases of these deficits remain poorly understood. Previous studies have demonstrated motivational deficits for palatable foods after sweet diet exposure during adolescence that might involve the dopamine (DA) system, a central actor in incentive processes. In the present study, the impact of adolescent sugar overconsumption on the sensitivity of the DA system was tested using pharmacological (Experiment 1) and receptor expression approaches (Experiment 2). Adolescent rats received free and continuous access to 5% sucrose solution from post-natal day 30–46. At adulthood, the functionality of the DA system in motivational processes was tested using systemic injections of specific DA receptors D1R or D2R agonists and antagonists during a motivation-dependent progressive ratio task (Experiment 1). Sucrose-exposed rats showed a lower motivation for saccharin and a decreased sensitivity to the effects of both D1R and D2R stimulation and blockade. In Experiment 2, Sucrose-exposed animals presented a lower expression of both D1R and D2R in the nucleus accumbens, a central brain region for incentive processes, but not in dorsal striatum or prefrontal cortex. These findings highlight the impact of sucrose overconsumption during adolescence on DA system that may support deficits in reward-related disorders.