Opposing Roles for Dopamine D2 and D3 Receptors on Neurotensin mRNA Expression in Nucleus Accumbens

Using in situ hybridization histochemistry in rat nucleus accumbens, we show that the dopamine D₃ receptor mRNA is expressed in the ventromedial part of the shell subdivision, where its gross distribution matches that of neurotensin mRNA. In addition, hybridization studies at the cellullar level show that a large fraction of the neurotensin neurons co-express the D₃ receptor mRNA in this restricted area. In contrast, the dopamine D₂ receptor mRNA is expressed mainly in the core and marginally in the shell, at the level of the cone. In rats treated by haloperidol and sulpiride, two D₂-like receptor antagonists, but not by SCH 23390, a D₁-like receptor antagonist, proneurotensin mRNA was increased in the D₂ receptor mRNA-rich areas but decreased in the D₃ receptor mRNA-rich areas. This suggests that the D₂ and D₃ receptors control neurotensin mRNA expression negatively and positively, respectively.