5-Lipoxygenase (5-LOX) is the enzyme metabolizing arachidonic acid to produce pro-inflammatory leukotrienes. We have reported that 5-LOX is translocated to the nuclear envelope after ischemic-like injury in PC12 cells. In the present study, we determined whether 5-LOX is activated (translocation and production of leukotrienes) after oxygen-glucose deprivation (OGD) in primary rat cortical neurons; if so, whether this activation is mediated by NMDA receptor. After OGD, 5-LOX was translocated to the nuclear envelope as detected by immunoblotting, immunostaining and green fluorescent protein-5-LOX transfection. 5-LOX metabolites, cysteinyl-leukotrienes (CysLTs) but not leukotriene B4, in the culture media were increased 0.5-1.5 h after recovery. Similarly, NMDA (100 microm) also induced 5-LOX translocation, and increased the production of CysLTs during 0.5-1 h NMDA exposure. Both OGD and NMDA reduced neuron viability. NMDA receptor antagonist MK-801 inhibited almost all the responses to OGD and NMDA; whereas 5-LOX activating protein inhibitor MK-886 and 5-LOX inhibitor caffeic acid inhibited the reduction of neuron viability and the production of CysLTs, but did not affect 5-LOX translocation. From these results, we conclude that OGD can activate 5-LOX in primary rat cortical neurons, and that this activation may be partly mediated via activating NMDA receptor.