OPPOSING ROLES FOR DOPAMINE D-2 AND D-3 RECEPTORS ON NEUROTENSIN MESSENGER-RNA EXPRESSION IN NUCLEUS-ACCUMBENS

Using in situ hybridization histochemistry in rat nucleus accumbens, we show that the dopamine D-3 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 cellular level show that a large fraction of the neurotensin neurons co-express the D-3 receptor mRNA in this restricted area. In contrast, the dopamine D-2 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 D-2-like receptor antagonists, but not by SCH 23390, a D-1-like receptor antagonist, proneurotensin mRNA was increased in the D-2 receptor mRNA-rich areas but decreased in the D-3 receptor mRNA-rich areas. This suggests that the D-2 and D-3 receptors control neurotensin mRNA expression negatively and positively, respectively.