[Identification of neuronal death and DNA fragmentation in early stage after rat transient forebrain ischemia]

To clarify whether programmed cell death plays an important role in the delayed neuronal death after forebrain transient ischemia, we investigated the relationship between pathological changes visualized by HE staining and intranuclear DNA fragmentation evaluated by the TUNEL method in rat hippocampal CA1 pyramidal neurons at early times after the onset of transient forebrain ischemia. The investigations were carried out in male Wistar rats (N = 22) subjected to 20 minutes of transient forebrain ischemia by Pulsinelli's method. No morphological changes or TUNEL staining were observed at 1 hour after forebrain ischemia. HE staining revealed morphological changes in 8 +/- 4%, 10 +/- 4% and 88 +/- 9% of neurons in hippocampus CA1 at 3, 6 and 24 hours after forebrain ischemia, respectively at which times 0%, 74 +/- 1% and 68 +/- 11% of the neurons showed marked labeling with the TUNEL method. We therefore conclude that DNA fragmentation as evaluated by the TUNEL method is not involved in neuronal death, and no DNA fragmentation was detectable prior to morphological changes in the early stage of forebrain ischemia.