Retinal axons in Xenopus show different behaviour patterns on various glial substrates in vitro.

Several lines of evidence suggest that glial cells have major effects on neuronal pathfinding. We have examined in vitro whether the outgrowth pattern of Xenopus retinal fibres is influenced by the glial cells encountered as they grow to the optic tectum. Strips of retina were cultured on monolayers of glial cells from the diencephalon and from the rostral and caudal ends of the optic tectum. On glia from the caudal end of the tectum the growth of fibres from the nasal and temporal ends of the strips was different: temporal fibres were shorter and more fasciculated than nasal fibres. This difference was still discernible on glia isolated from the rostral end of the tectum, but to a lesser extent. On glia from the diencephalon there was no difference between nasal and temporal fibres.