Neuron-specific and non-neuronal enolase in developing chick brain and primary cultures of chick neurons.

Developmental changes of the neuron-specific enolase (NSE) and the non-neuronal enolase (NNE) were determined in pure neuronal, or mixed cultures of neuronal and glial cells, prepared from brains of 8-day-old chick embryos, as a function of cellular development with time in culture. The modifications observed in culture were compared to those measured in brain during the development of the nervous tissue in the embryo and during the post-hatching period. In the whole brain, the total enolase activity increases progressively until the adult level, the NSE appears only 4 days before hatching. The total enolase activity of pure neurons increases until 8 days of culture but the NSE never appears during this period. Mixed cultures of neurons and glial cells present an increase of total activity until 14 days of culture and neuron-specific form of the enzyme can be observed after 6 days of culture. Our results suggest that NSE appears only in the functional brain and is expressed in cultivated neurons only when glial cells are present simultaneously.