Growth cones of dorsal root ganglion but not retina collapse and avoid oligodendrocytes in culture.

Axons in the central nervous system of mature mammals generally fail to regenerate following injury. Although the reason for this regenerative failure remains unknown, several lines of evidence suggest that it is due to nonpermissiveness of oligodendrocytes for axonal elongation. However, most of the in vitro experiments carried out so far used neural-crest-derived peripheral neurons to test the permissiveness of oligodendrocytes, although studying the interactions between central neurons and oligodendrocytes is crucially important for elucidating their roles in vivo. In this study we cultured retinas and dorsal root ganglia of the chick embryo with oligodendrocytes obtained from postnatal rat spinal cord and performed time-lapse analysis. Oligodendrocytes were identified with galactocerebroside antibody. Retinal growth cones readily grew over oligodendrocytes, while growth cones of the dorsal root ganglion collapsed and grew away on contacting the oligodendrocytes. Correspondingly, neurite-free areas centered by oligodendrocytes were formed behind growth cones in DRG-oligodendrocyte but not in retina-oligodendrocyte co-culture. These observations suggest the possibility that responsiveness of growth cones to oligodendrocytes is dependent on neuronal type.