Astroglial reaction in the gray matter lumbar segments after midthoracic transection of the adult rat spinal cord

Previous studies of cordotomized rats revealed a glial reaction in the gray matter of the spinal cord at sites remote from the lesion, and the present study was done to explore this phenomenon further. Seventy-five young adult female rats were cordotomized and 10 hemicordotomized, both operations at T5. Between 1 and 28 days postoperatively, histologic sections of thoracic and lumbar segments stained by phosphotungstic acid hematoxylin (PTAH, pH 2.37), by periodic acid Schiffdimedon (PAS-D) or by an immunocytochemical method for glial fibrillar acidic protein (GFAP) revealed histological changes as follows: PTAH staining showed that astroglia in thoracic and lumbar regions of the cordotomized rats possessed a swollen, pink-staining cytoplasm and enlarged, thick, dark blue-staining fibrous processes. This response, first noted within 4 days, had intensified by 7 days and was maximal at 14 to 17 days postoperatively. By 28 days, the reaction had diminished but was still readily detectable. The more specific GFAP staining procedure confirmed that the reactive cells were astrocytes and demonstrated that their fibrillar density had increased. The PAS-D reaction revealed glycogen accumulation in glia of the lumbar gray matter within 2 days; this response intensified by 4 days and diminished to normal by 14 days. This reaction was largely concentrated in the perivascular end feet of astroglia, but also appeared in conjunction with perineuronal astroglia. The site of glial reactivity included both dorsal and ventral horns and was particularly noticed in the gray matter surrounding the central canal. In the hemicordotomized rats, the thoracic and lumbar glia response was much more pronounced ipsilaterally than contralaterally. These results support the interpretation that an astroglial response, involving hypertrophy, fibrillogenesis, and glycogen accumulation, occurs in response to degenerating nerve fibers caudal to sites of spinal cord injury.