Regrowth of dorsal root axons into a radiation-induced XXXX environment in the spinal cord.

@entity35 @entity3505 @entity3698 @entity942
Exposure of the lumbosacral spinal cord of early postnatal @entity35 to X-rays reduces the glial populations within the irradiated region. The present study examines the ability of axons of a dorsal root subjected to a crush-freeze lesion to grow back into this @entity942 spinal cord environment, in contrast to the non-irradiated @entity35 . Ultrastructural examination of the dorsal root entry zone (DREZ) 60 days after root injury revealed a well-formed astrocytic scar in this zone and adjacent regions of spinal cord in non-irradiated @entity35 . In contrast, scar formation did not occur in irradiated root-lesioned animals in which the astrocytic response was quite limited. Axons were present in the DREZ and underlying spinal cord in irradiated root-lesioned @entity35 at this time but were absent from these regions in the non-irradiated lesioned controls. These ultrastructural findings are highly suggestive that axons are capable of regrowth into the irradiated spinal cord. Axonal regrowth was assessed further by tracing techniques after application of a combination of @entity3698 -labeled @entity3505 germ agglutinin and horseradish @entity3698 to the cut end of the root distal to the previously injured site. Labeled axons were readily identified within the spinal gray matter in irradiated lesioned but not in the non-irradiated lesioned @entity35 . These data, together with the ultrastructural observations, are supportive of regrowth of the dorsal root axons into the spinal cord. The radiation-induced changes in the glial populations are discussed with regard to conversion of a normally non-permissive environment into one conducive for axonal regrowth.
