['Ischemic tolerance' in ischemia-reperfusion injury in the optic nerve in rats].

Brief ischemia caused by high intraocular pressure induced tolerance to subsequent ischemia-reperfusion injury in rats. Male Wistar rats were subjected to 15 minutes of ischemia. This ischemic injury did not show distinct axonal damage in the optic nerve in electron microscopy. 1, 2, 4, 7, and 14 days after the first 15 min ischemia, the rats were subjected to a second ischemia for 45 minutes (ischemic tolerance). After 1 week, the rats were perfusion fixed and the optic nerves were processed for light and electron microscopy. Samples of the axonal density in the central optic nerve 2 mm behind the lamina cribrosa were observed and counted an electron micrographs. In axonal morpometric findings, 2 days and more after brief ischemia, the damage was lessened more than after 45 minutes ischemia (control) and the difference was significant. This 'ischemic tolerance' induced by brief ischemia might be considered the same stress as brain ischemia-reperfusion injury.