The growth inhibitor factor (GIF) is a new member of the metallothionein family that is downregulated in Alzheimer's disease brain. Using a confocal laser scan microscope with polyclonal and monoclonal antibodies to GIF, and monoclonal antibodies to glial fibrillary acidic protein (GFAP) and MAP-2, we demonstrated that GIF immunoreactivity was expressed primarily in astrocytes and much less in neurons. In astrocytes of normal rat brain GIF immunoreactivity was detected mainly in the cell bodies, while GFAP immunoreactivity was detected mainly in the processes. GIF immunoreactivity was more strongly expressed in reactive astrocytes. These findings were confirmed with both polyclonal and monoclonal antibodies. Following stab wounds, a number of GIF-positive reactive astrocytes were detected around the wounds at 3 days postoperation. After 7 days GIF immunoreactivity was detected in cell bodies and processes of reactive astrocytes. The number of GIF-positive astrocytes and the intensity of the immunoreactivity remained elevated over the control levels at least through 28 days. These immunocytochemical findings correlated well with changes in GIF protein and mRNA levels. Not only changes in GIF protein and mRNA levels but also intracellular localization of GIF in normal rat brain and after stab wounds in rat brain were different from those of GFAP. These results support the concept that GIF plays an important role in the processing of reconstruction after brain damage.