ESTABLISHMENT OF HIGHLY ENRICHED TYPE-2 ASTROCYTE CULTURES AND QUANTITATIVE-DETERMINATION OF INTENSE GLUTAMINE-SYNTHETASE ACTIVITY IN THESE CELLS

We report procedures that allow one to develop and maintain cultures highly enriched in rat neopallial type-2 astrocytes. Even after four weeks such cultures consist of more than 90% type-2 astrocytes, approximately 5% O-2A progenitors and fewer than 2% type-1 astrocytes. Their survival for more than 5 days requires the addition of conditioned medium from type-1 astrocyte cultures. The type-2 astrocytes have an intense glutamine synthetase activity whose basal level is sevenfold higher than in type-1 astrocytes. The glutamine synthetase activities of both the type-2 and type-1 astrocytes are increased after exposure to cortisol. Thus, type-2 astrocytes express the two quint-essential astrocytic features: glial fibrillary acidic protein (previously reported by others) and glutamine synthetase.