Glutamate agonists have been shown to stimulate striatal. dopamine release, but less is known about dopamine-glutamate interactions at the receptor level. We treated rats with 0.3, 1.0, or 3.0 mg/kg of MK-801, an NMDA antagonist, daily for 1 week and, using in situ hybridization, measured dopamine receptor mRNA levels in cortical and subcortical structures. MK-801 caused a significant increase of D1 and D2 mRNA in the dorsal and ventral striatum, a significant decrease of D3 mRNA in the nucleus accumbens, and a significant decrease of D1 mRNA in the limbic cortex. Dopamine autoreceptor expression, reflected by D2 mRNA in the midbrain, was increased in the ventral tegmental area, but not in the substantia nigra. Thus, MK-801 appears to differentially regulate the mesocorticolimbic and nigrostriatal dopamine systems.