BDNF-dependent stimulation of dopamine D5 receptor expression in developing striatal astrocytes involves PI3-kinase signaling

It is well known that brain-derived neurotrophic factor (BDNF) and the early nigrostriatal dopaminergic input are implicated in the regulation of developmental processes in the neostriatum. There is growing evidence that interactions between these developmental signals rather than singular actions are critical for cellular differentiation and compartmentation of the striatum. In the present report, our goal is to identify striatal target cells for BDNF and dopamine. Using primary neuronal and astroglial cell cultures, we have demonstrated that BDNF selectively regulates D-5 but not D-1 receptor expression in astrocytes. This effect was not observed in neurons. Pharmacological approaches indicated that BDNF effects on dopamine D-5 receptor expression were mediated at the intracellular level by an activation of the PI3- but not MAP-kinase cascade. FACS analysis and confocal laser microscopy revealed that the newly synthesized D-5 receptors were integrated into the plasma membrane of astrocytes. Our findings clearly show that developing striatal astrocytes are targets for BDNF. Furthermore, BDNF appears to regulate the dopamine responsiveness of astrocytes. This implicates that functional interactions between BDNF, dopamine, and astrocytes are necessary to warrant proper differentiation of the striatal anlage. (C) 2004 Wiley-Liss, Inc.