A novel way of removing quiescent astrocytes in a culture of subcortical neurons grown in a chemically defined medium.

A new method has been described for removing a very small number of contaminating astrocytes in neuronal cultures (derived from the septal-diagonal band region of 17-day-old embryonic rat brain) grown in a chemically defined medium. The proportion of these glial fibrillary acidic protein (GFAP)-positive cells was usually less than 1.5% up to 10 days, but thereafter their number increased rapidly reaching 10-15% by 22 days in vitro. A prolonged exposure to normally used concentration of cytosine arabinoside (Ara-C; 10 microM) was toxic to both astroglial and neuronal cells, while a brief treatment (48 h) with a low level (4 microM) of Ara-C failed to eliminate these astrocytes, as judged by glutamine synthetase activity and GFAP-positive cell count. However, these quiescent astroglial cells could be easily eliminated if they were induced to proliferate by epidermal growth factor before exposure to Ara-C. The combined treatment with these agents had no effect on the number of acetylcholinesterase-positive cells, and on the development of cholinergic and GABA-ergic neurons, as measured in terms of choline acetyltransferase and glutamate decarboxylase activity, respectively.