Immunohistochemical localization of ubiquitin in gerbil hippocampus with induced tolerance to ischemia.

Using immunohistochemistry, we visualized the localization of ubiquitin in the gerbil hippocampus following 3 min of ischemia with or without pretreatment with 2 min of sublethal ischemia and 3 days of reperfusion. Ubiquitin immunoreactivity in the hippocampus disappeared 4 h after 3 min of ischemia both with and without pretreatment. The immunoreactivity in the CA3 and the dentate gyrus recovered by 24 h, but never recovered in the CA1, where delayed neuronal death takes place, without pretreatment. However, the pretreatment, which protects against CA1 neuronal damage, led to recovery of ubiquitin immunoreactivity in the CA1 by 48 h. Thus, recovery of ubiquitin may be a prerequisite to neuronal survival after ischemia and the role of ubiquitin in ischemic tolerance was suggested.