Effects of adolescent social isolation on motivation for sucrose: Evidence from demand and choice procedures

Adolescent social isolation is a developmental stressor associated with behavioral alterations, heightened stress reactivity, and increased vulnerability to substance use disorders. Preclinical studies consistently show that isolation increases the rewarding properties of drugs, resulting in greater consumption and drug-seeking behavior. However, whether similar effects extend to non-drug reinforcers, such as sucrose, remains unclear. In the present study, male rats were reared either in social isolation or group housing during adolescence, and sucrose reward sensitivity was assessed in adulthood. First, animals were evaluated in a sucrose preference task in which they had free access to a sucrose solution and water for two hours. Reward sensitivity was then assessed to determine whether isolation altered (a) sucrose-seeking behavior under increasing operant requirements (demand analysis) or (b) choice behavior between sucrose options delivering different reinforcement rates under concurrent schedules. Isolated rats consumed more sucrose in the free-access task than group-housed rats. However, no group differences were observed in demand elasticity or sensitivity to differences in reinforcement rates during the choice task. These findings suggest that the effects of adolescent social isolation on sucrose reward may be limited to consummatory behavior, without altering appetitive or effort-related aspects of motivation. Overall, the results support the view that the effects of adolescent social isolation might be specific to drug-related rewards and their underlying neural mechanisms than to reward processing in general.