The interaction of Schwann cells with CNS axons in regions containing normal astrocytes.

On occasions retinal axons can be myelinated by Schwann cells. In the present experiments cultured autologous Schwann cells were injected into the optic disc of adult cats and the extent of Schwann cell myelination determined. Little if any Schwann cell myelination of retinal ganglion cell axons developed. Schwann cells were also injected into lesions in the cerebral cortex induced by ethidium bromide. In this site some Schwann cell remyelination was detected, but it was restricted to areas next to regions of malacia induced by the injection procedure. It was concluded that astrocyte responses, limit Schwann cell myelination and remyelination in normal tissue by excluding Schwann cells from the CNS compartment, and induce changes in chronically demyelinated and amyelinated axons which may affect myelination.