Accumbens dopamine mechanisms in sucrose intake

Extracellular levels of dopamine (DA) and monoamine metabolites were measur ed in the nucleus accumbens (NAcc) during sucrose licking using microdialys is in freely moving rats. The converse relationship also was tested. Using bilateral reverse microdialysis, D1 and D2 receptor antagonists (SCH23390, sulpiride) and the DA uptake blocker nomifensine were introduced into NAcc while measuring both ingestive behavior and neurochemistry. Licking of 0.3 M sucrose caused a 305% (+/- 69%) increase in NAcc DA compared with water i ntake. Reverse microdialysis of nomifensine at a dose that increased accumb ens DA levels (1484 +/- 346%) led to an increase of sucrose intake (152.5 /-5.4%). Concurrent infusions of the D1 and D2 blockers with nomifensine br ought sucrose ingestion back near to control levels (114.8 +/-3.7%). The hi gher dose of the D2 antagonist sulpiride also increased DA levels and sucro se intake. In contrast, the lower dose of the D2, and both doses of the D1 antagonist had no chemical or behavioral effects. These results showed rele ase of NAcc DA in response to sucrose licking and the converse, an augmenta tion of the behavior by uptake blockade. The same data, however, failed to prove that tonic, local accumbens D1 and D2 receptor activity influenced th is ingestive behavior. (C) 2001 Elsevier Science B.V. All rights reserved.