Localization of multiple dopamine receptor subtype mRNAs in human and monkey motor cortex and striatum

Dopamine plays a critical role in motor and cognitive function through actions mediated by specific receptors, multiple subtypes of which have recently been identified. The distribution of mRNAs encoding D1, D2 and D5 receptors in the motor cortex of humans and in the motor cortex and striatum of macaque monkeys was examined using in situ hybridization. In motor cortices from both primate species, hybridization to each receptor probe resulted in numerous labeled cells throughout layers II-VI. In contrast to neocortex, in monkey striatum only the D1 and D2 receptor probes showed significant hybridization. Thus, not only does primate neocortex possess a broader representation of the dopamine receptor subtype mRNAs examined in comparison with striatum, but the unexpected presence and widespread distribution of D2 and D5 receptor mRNAs in cortex suggests that, along with D1 receptors, D2 and D5 receptors play a crucial role in the dopaminergic modulation of cognition and motor behavior, and in dopamine dysfunction associated with neuropsychiatric disorders.