When cultured astrocytes are treated with agents that elevate intracellular cyclic AMP, they become process-bearing stellate cells. In the present study, we investigated possible developmental changes of astrocyte stellation induced by β-adrenoceptor stimulaton. Cultured astrocytes were prepared from the cerebral cortices of embryonic day 18 (E18) and postnatal day 2 (P2) rats. Treatment with the β-adrenoceptor agonist isoproterenol induced stellation in P2 astrocytes more potently and rapidly than in E18 astrocytes. Isoproterenol-stimulated increase in cellular cyclic AMP levels was very similar in E18 and P2 astrocytes. The membrane-permeable cyclic AMP analog dibutyryl cyclic AMP induced stellation in P2 astrocytes more potently and rapidly than in E18 astrocytes. Stellation induced by the protein kinase C activator phorbol ester was not different between E18 and P2 astrocytes. These results suggest that β-adrenoceptor-mediated astrocyte stellation increases during development and that this change is attributed to the development of mechanisms downstream from cyclic AMP production.