In-vitro studies using cultured brain cells are hampered by the fact that these cells are exposed to high concentration of growth factors from fetal calf serum (FCS) as well as from artificial media. Therefore, they are often in an undifferentiated state and not necessarily representative for a functional cell in-vivo. Possible cAMP involvement in cellular differentiation was examined in cultured cells exposed to either forskolin or dBcAMP. The evaluation of cellular thymidine incorporation and cAMP production serve to determine the action of these agents. GFAP was used on a measure of glial differentiation. All three cell types showed a forskolin dose-dependent reduction of thymidine incorporation in the presence of FCS. Maximal inhibition was achieved with 100muM forskolin which reduced thymidine incorporation to levels otherwise found in the absence of FCS (75-95% reduction). 5-day exposure of glial cells to forskolin not only caused striking morphological changes similar to those observed after dBcAMP but also led to an increased expression of GFAP which was demonstrated by immunohistochemistry and ELISA. These findings stress the importance of cAMP in the regulation of mitotic activity. Moreover, the results suggest that forskolin may serve as a tool to initiate differentiation in brain cells in culture.
