Society for neuroscience, Society for neuroscience
Although interference with the dopamine (DA) systems has been shown to impair instrumental behavior, it may have a little or no effect on the basic processes of motivation (Salamone, 1992). The present study was designed to directly examine the effects of DA receptor antagonists on licking in a choice situation. The food-deprived rats were trained to lick for the solution from either a high-positioned 20% sucrose or the low-positioned 15% sucrose. After 10 to 14 sessions of training, the subject significantly preferred to consume the high-positioned 20% sucrose solution. Drug treatment was conducted by IP injection of SCH23390 (0.05, 0.1, 0.2 mg/kg), raclopride (0.1, 0.2 mg/kg), or haloperidol (0.05, 0.1 mg/kg). While the licking of high-positioned 20% sucrose was dose-related suppressed by all three drugs, the concurrent consumption of the low-positioned 15% sucrose was significantly enhanced. However, a more experience of licking on the low-positioned liquid was required for the subject to produce such a behavioral reallocation under raclopride and haloperidol treatments, but not under SCH23390. These results indicate that the motivational processing can be adjusted to counteract behavioral changes under DA receptor blockade.