ASTROCYTE REACTIVITY IN NEONATAL MICE - APPARENT DEPENDENCE ON THE PRESENCE OF REACTIVE MICROGLIA MACROPHAGES/

In neonatal mice, an acute injury produced by a stab wound to the cort ex results in minimal astrocyte reactivity, as has been observed by ot hers. However, if the source of the stab wound, a piece of nitrocellul ose (NC) membrane, were now implanted in the cortex for a period of ti me (chronic NC implant injury), then extensive astroglial reactivity i n the neonatal brain ensues. The astrogliosis is manifested by increas ed mRNA, protein content, and immunoreactivity for GFAP, and by ultras tructural changes. Given the previous reports that inflammatory cytoki nes are possible mediators of astrocyte reactivity (e.g., Balasingam e t al: J Neurosci 14:846, 1994), we examined the brain parenchyma of ne onatal mice following an NC stab or implant injury, with minimal or ex tensive astrogliosis, respectively, for a possible differential repres entation of inflammatory cells. A significant correlation (r = 0.87, P < 0.05) was observed between the occurrence of astrogliosis and the p resence of reactive microglia/macrophages; no other inflammatory cell type was detected in the brain parenchyma of neonatal mice following N C implant injury. We suggest that reactive microglia/macrophages are r equired for the evolution of cells into reactive astrocytes following insults to the neonatal brain. (C) 1996 Wiley-Liss, Inc.