Arachidonic acid metabolites contribute to the irreversible depolarization induced by in vitro ischemia.

Intracellular recordings were made from hippocampal CA1 neurons in rat slice preparations. Superfusion with oxygen- and glucose-deprived medium (in vitro ischemia) produced a rapid depolarization approximately 5 min after the onset of the superfusion. Even when oxygen and glucose were reintroduced immediately after rapid depolarization, the membrane depolarized further (persistent depolarization) and reached 0 mV (irreversible depolarization) after 5 min from the reintroduction. The pretreatment of the slice preparation with a phospholipase A2 (PLA2) inhibitor, para-bromophenacyl bromide, or a cytochrome p-450 inhibitor, 17-octadecynoic acid, significantly restored the membrane to the preexposure potential level after the reintroduction of oxygen and glucose. The administration of 14,15-epoxyeicosatrienoic acid or 20-hydroxyeicosatetraenoic acid did not change the latency of the rapid depolarization and did not allow the membrane potential to recover after the ischemic exposure. In contrast, after pretreatment with cyclooxygenase or lipoxygenase inhibitors, such as indomethacin, resveratrol, Dup-697, nordihydroguaiaretic acid, and 3,4-dihydrophenyl ethanol, a minority of neurons tested showed postischemic recovery from the persistent depolarization. Improved recovery was also seen after treatment with the free radical scavengers, edaravone and alpha-tocopherol. These results suggest that the activation of the arachidonic acid cascade via PLA2 and the free radicals produced by arachidonic acid metabolism contribute to the irreversible depolarization produced by in vitro ischemia.