Expression of nerve growth factor in astrocytes of the hippocampal CA1 area following transient forebrain ischemia

We have examined by immunoassay and immunohistochemistry, the expression of nerve growth factor in the rat hippocampus, one to 28 days after transient forebrain ischemia. In the CA1 area, the overall level of nerve growth fac tor expression remained constant over the first three days of reperfusion w hile it increased by about 45% of control levels after longer postischemic periods. In contrast, a slight decrease in nerve growth factor levels, whic h was most prominent at three days postlesion, was observed in the other hi ppocampal regions. Immunohistochemical analysis of the distribution of nerv e growth factor showed that its expression was up-regulated in astrocytes b ut not in microglia of the postischemic CAI region and that the intensity a nd temporal profile of the changes in nerve growth factor immunostaining in these cells, was consistent with that observed in the immunoassay. Interes tingly, the regulation of the nerve growth factor expression in reactive as trocytes of the postischemic CA1 area closely parallels that of kainate rec eptor subunits GluR5-7, raising the possibility of a cause-effect relations hip. These results indicate that after ischemia nerve growth factor expression i s up-regulated in reactive astrocytes suggesting that these cells may contr ibute to rescuing damaged neurons by means of increasing nerve growth facto r production. (C) 1999 IBRO. Published by Elsevier Science Ltd.