Fos-like immunoreactivity in rat hippocampal neurons following transient global ischemia.

Immediate early genes are expressed following ischemia in many tissues including the brain. Using a chest compression global ischemia model that produced delayed neuronal degeneration in surviving rats, we examined the hippocampal Fos response to ischemia/reperfusion by immunohistochemistry and electron microscopy. Immunostained nuclei were seen in a few CA1 pyramidal cells 1-3 h after reperfusion while the entire dentate granular cell population was immunoreactive. By electron microscopy, subcellular Fos-like immunoreactive sites were found both in the cell nuclei and on segments of endoplasmic reticulum. These findings indicate that transient global ischemia differentially affects the early response genes in neurons of the hippocampal subfields and that such difference may be related to the adult neuroplasticity of the brain.