Regionally distinct regulation of astroglial neurotransmitter receptors byfibroblast growth factor-2

Fibroblast growth factor (FGF)-2 is an abundant astroglial cytokine. We hav e previously shown that FGF-2 down-regulates gap junctions in primary astro glial cultures (B. Reuss et al., 1998, Glia 22, 19-30). We demonstrate now that FGF-2 induces astroglial dopamine (DA) sensitivity and D1 dopamine-rec eptor (D1DR) antigen and message in cortical and striatal astroglial cultur es. On the functional level 10 mu mol/L DA triggered transient increases in astroglial [Ca2+](i). In gap-junction-coupled cells, no FGF-2-dependent ch anges in proportions of DA-responsive cells were observable. However, uncou pling with octanol or 18 alpha-glycirrhetinic acid isolated the smaller pop ulation of astrocytes intrinsically sensitive to DA which was significantly increased by FGF-2 in cortical and striatal cultures. Administration of DR -specific substances revealed that FGF-2 upregulated D1DR. These results in dicate that downregulation of astroglial gap junctions by FGF-2 is accompan ied by an upregulation of D1DR and DA sensitivity, adding a new aspect to t he role of FGF-2 in the regulation of brain functions.