ASTROCYTE EXPRESSION OF D2-LIKE DOPAMINE RECEPTORS IN THE PREFRONTAL CORTEX

The dopaminergic system is of crucial importance for understanding human behavior and the pathogenesis of many psychiatric and neurological conditions. The majority of studies addressing the localization of dopamine receptors (DR) examined the expression of DR in neurons, while its expression, precise anatomical localization and possible function in glial cells have been largely neglected. Here we examined the expression of D2-like family of DR in neuronal and glial cells in the normal human brain using immunocytochemistry and immunofluorescence. Tissue samples from the right orbitomedial (Brodmann's areas 11/12), dorsolateral (areas 9/46) and dorsal medial (area 9) prefrontal cortex were taken during autopsy from six subjects with no history of neurological or psychiatric disorders, formalin-fixed, and embedded in paraffin. The sections were stained using novel anti-DRD2, anti-DRD3, and anti-DRD4 monoclonal antibodies. Adjacent sections were labeled with an anti-GFAP (astroglial marker) and an anti-CD68 antibody (macrophage/microglial marker). The pyramidal and non-pyramidal cells of all three regions analyzed had strong expression of DRD2 and DRD4, whereas DRD3 were very weakly expressed. DRD2 were more strongly expressed in layer III compared to layer V pyramidal neurons. In contrast, DRD4 receptors had a stronger expression in layer V neurons. The most conspicuous finding was the strong expression of DRD2, but not DRD3 or DRD4, receptors in the white matter fibrous astrocytes and in layer I protoplasmic astrocytes. Weak DRD2-immunoreactivity was also observed in protoplasmic astrocytes in layers III and V. These results suggest that DR-expressing astrocytes directly participate in dopaminergic transmission of the human prefrontal cortex.