Astrocyte-regulated synaptogenesis: 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. Dendrites developing in homotopic co-cultures could reach a state of maturation allowing the establishment of synapses with axons from mesencephalic explants. This culture system thus partially reproduces the in vivo conditions in which striatal neurons developing in an homotopic glial environment can serve as synaptic targets for afferent mesencephalic axons.

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.

In vitro regulation of neuronal morphogenesis and polarity by astrocyte-derived factors.

Mesencephalic neurons were cultured from 2 to 5 days in mesencephalic (CM Gmes) or striatal (CM Gstr) astrocyte conditioned media or in the soluble (S100) and insoluble (P100) fractions prepared from these media by ultracentrifugation. CM Gmes as well as all soluble fractions induced dendritic and axonal elongation, whereas CM Gstr and the insoluble fractions promoted axonal growth only. The study of the shape of the neuronal cell bodies and the measurement of their adhesion to the substratum revealed that axons elongated under low adhesion conditions, but that dendrite growth was highly dependent upon adhesion and spreading of the neuronal soma.

Cyclic AMP reduces adhesion of isolated neuronal growth cones from developing rat forebrain to an astrocytic cell line from embryonic mouse striatum.

We have recently shown that isolated neuronal growth cones from developing rat forebrain possess an appreciable activity of adenylate cyclase, producing cyclic adenosine monophosphate, which can be stimulated by various neurotransmitter receptor agonists and by forskolin [Lockerbie R. O., Hervé D.

Region-specific neuro-astroglial interactions: ultrastructural study of the in vitro expression of neuronal polarity.

Mesencephalic neurons were cultured for 2 days on mesencephalic or striatal astrocyte monolayers. The morphology of these neurons was studied in electron microscopy. The number of dendritic profiles was higher on mesencephalic astrocytes (homotopic neuro-astroglial co-cultures) than on striatal astrocytes (heterotopic co-cultures).