Astrocyte-regulated GABA-ergic striatal neurons development: an in vitro ultrastructural study

Striatal neurons from E15 rat embryos were dissociated, plated at low cell density on polyornithine or on astrocyte monolayers derived from the striatum (homotopic) or mesencephalon (heterotopic), and cultured in a chemically defined medium. After 2 to 10 days neurons could be divided in 3 classes according to their cell body diameter: small, medium or large. The percentage of small neurons which was very high 60% for GABAergic neurons on polyornithine after 2 days in vitro was reduced to 35% on mesencephalic astrocytes and to less than 20% on striatal astrocytes. The decrease in the number of small cells was paralleled by an increase in the number of multipolar medium size cells whereas the percentages of bipolar medium size and large neurons remained constant (55 and 4% respectively). All results obtained with the general neuronal population were replicated with the GABAergic sub-population which accounted for more than 50% of total neuronal population. These experiments confirm the beneficial influence of homotopic astrocytes on neuronal differentiation and on dendrite growth.