CAMP-induced stellation in primary astrocyte cultures with regional heterogeneity

It is well known that increased cAMP levels in cultured astrocytes can conv ert flat polygonal shaped astrocytes into process-bearing. stellate astrocy tes. In this study, we have examined the possible existence of astrocyte re gional heterogeneity in morphological changes in response to cAMP stimulati on. Primary astrocyte cultures were prepared from six different regions of neonatal rat brains, including cerebral cortex, hippocampus, brain stem, mi d brain, cerebellum, and hypothalamus. After about 2 weeks in culture, the astrocyte culture medium was changed to DMEM containing various concentrati ons of 8-CPT-cAMP, a membrane permeable cAMP analog,for 2 h. We found that 250 muM 8-CPT-cAMP produced a maximum effect causing >95% stellation in all regional astrocytes except hypothalamic astrocytes (56% stellation). At lo wer cAMP concentrations, cell stellation most effectively occurred in cereb ellar astrocytes. To examine further the regional heterogeneity of astrocyt e morphological changes, glutamate was added together with 8-CPT-cAMP to bl ock cAMP-induced astrocyte stellation. Interestingly, glutamate blockage on cAMP-induced astrocyte stellation was brain region-specific in that cerebr al and hippocampal astrocytes were effectively blocked by glutamate when co mpared to other regional astrocytes. Furthermore, glutamate inhibited isopr oterenol-induced astrocyte stellation in a region-specific manner similarly as in cAMP-induced stellation. The present study demonstrates that astrocy tes derived from different regions of the neonatal rat brain maintain diffe rent levels of morphological plasticity in culture. (C) 2000 Elsevier Scien ce B.V. All rights reserved.