The CCK-1-receptor deficient Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats are hyperphagic and exhibit a greater preference for sucrose compared to lean controls (LETO). To directly assess motivation to work for sucrose reward in this model of obesity and type-2 diabetes, we examined the operant performance of OLETF rats at non-diabetic and prediabetic stages (14 and 24 weeks of age, respectively) on fixed-ratio (FR) and progressive-ratio (PR) schedules of reinforcement. To evaluate the involvement of dopamine systems, the effects of the D1 receptor antagonist, SCH23390 (100, 200 nmol/kg, IP), and the D2 receptor antagonist, raclopride (200, 400 nmol/kg, IP), also were tested on PR responding for sucrose. Compared to age-matched LETO rats, 14-week old OLETF rats emitted more licks on the "active" empty spout operant on the FR-10 schedule of reinforcement to obtain 0.01M and 0.3M sucrose and completed higher ratio requirements on the PR schedule to gain access to 0.3M and 1.0M sucrose. At 24 weeks, this effect was limited to 1.0M sucrose. Both antagonists were potent in reducing operant responding to 0.3M sucrose in both strains at both ages and there was no strain effect to SCH23390 at either age. OLETF rats, on the other hand, showed an increased sensitivity to the higher dose of raclopride, resulting in reduced responding to sucrose reinforcement at 24 weeks. Taken together, these findings provide the first direct evidence for an increased motivation for sucrose reward in the OLETF rats, and suggest altered D2 receptor regulation with the progression of obesity and prediabetes.