Biochemical and immunocytochemical changes in glial fibrillary acidic protein after sab wounds

Abstract

Changes of glial fibrillary acidic protein (GFAP) in the forebrain of rats with stab wounds were determined by quantitative immunoblots and by immunohistochemistry. Bilateral stab wounds were made stereotaxically in the cortex and hippocampus. In control rats, the scalp was retracted and depressions were etched on the intact skull. At various times up to 21 days postoperation, one cerebral hemisphere was homogenized, proteins were separated by polyacrylamide gel electrophoresis and immunoblots were quantitated by densitometry. The contralateral hemisphere was immunostained for GFAP. Three hours postoperation GFAP + cells were detected around the wound but there was no increase of total GFAP. At 6 h postoperation total GFAP in the fore brain decreased to 80% of the sham-operated control value and the number of GFAP + cells was lower, compared to the controls, in layer 1 of the cortex, corpus callosum, cingulum, external capsule, internal capsule, hippocampus, optic tracts and around blood vessels. This early relative decrease in GFAP levels was actually due to an increase in GFAP in the sham-operated controls, which mounted a stronger gliotic response during the first 24 h. In neither group of animals did the GFAP levels drops below those of intact unoperated animals. At 24 h total GFAP began to increase. The number and intensity of reactive glia in the vicinity of the wound increased steadily, appearing to reach a maximum at about 7 days, then declining significantly by 21 days. The glial reaction was most pronounced in the hippocampus. Total GFAP reached 180% of the control value by 7 days and then declined to 117% by 21 days. The resolution of reactive gliosis and the changes in GFAP content were much faster than we observed in experimental autoimmune encephalomyelitis. The decreased ratio of GFAP levels in operated animals over sham-operated controls at 6 and 12 h was unexpected and may be due to more severe anoxic and ischemic damage and stress-related suppression of protein synthesis occurring in operated animals.