Neurons are generated in confluent astroglial cultures of rat neonatal neocortex

Cells of the telencephalon are generated in specific proliferative zones from which neuronal and glial precursors migrate to their destinations. Recent evidence indicates that some precursors do not turn into differentiated cells but keep their ability to proliferate. Here, we report that neurons can originate in primary cultures of astroglial cells prepared from neocortex of newborn rats. The first neuronal cells appeared shortly before confluence, when a glial monolayer was being formed. After confluence, these still undifferentiated cells increased in number. Later, they became immunohistochemically positive for the neuron-specific marker microtubule-associated protein 2a,b. They also contained neurofilament-L protein as well as the specific messenger RNA coding for neurofilament-H. The observation that they took up bromo-deoxyuridine indicated that they synthesized DNA, i.e. they proliferated. When Dulbecco's modified essential medium was substituted with fetal calf serum, the appearance of neurons depended on the seeding density of the dispersed cells. This was no longer the case, when the cultures were maintained in Dulbecco's modified essential medium/F12 medium to which transferrin, insulin and selenium chloride had been added. It is concluded that neuronal precursors can survive in primary astroglial cultures. After confluence of the astroglial cells the precursors proliferate if appropriate conditions are present. Our observation provides a new model for the investigation of cultured neurons and neuronal-glial interactions.