Cyclooxygenase-2 mediates the development of cortical spreading depression-induced tolerance to transient focal cerebral ischemia in rats

We examined the role of cyclooxygenase-2 in the development of ischemic tolerance induced by cortical spreading depression against transient, focal brain ischemia. Cortical spreading depression was continuously induced for 2 In with topical KCl (13 +/- 1 depolarizations/2 h) in male Wistar rats. At 1, 2, 3, 4, and 5 days following recovery, the middle cerebral artery Was transiently occluded for 120 min. Four days later, the animals were killed and infarct volume was determined. Additionally, cyclooxygenase-2 levels in the cerebral cortex and 15 deoxy-Delta(12, 14) PGJ(2) levels in cerebrospinal fluid were determined at these times with Western blotting and immunoassay, respectively. Infarct volume was reduced compared with non-cortical spreading depression control animals (274.3 +/- 15.3 mm(3)) when cortical spreading depression was performed 3 and 4 days before middle cerebral artery occlusion (163.9 +/- 14.2 mm(3), 154.9 +/- 14.2 mm(3)) but not at 1, 2 and 5 days (280.4 +/- 17.3 mm(3) 276.3 +/- 16.9 mm(3) and 268.5 +/- 17.3 mm(3)). Cyclooxygenase-2 levels increased most dramatically starting at 2 days, peaked at 3 days, and started to return toward baseline at 4 days after cortical spreading depression. 15 Deoxy-A(12, 14) PGJ2 levels increased from 134.7 +/- 83 pg/ml at baseline to 718 +/- 98 pg/ml at 3 days. Administration of N-[2-cyclohexyloxy-4-nitrophenyl] methane-sulphonamide (10 mg/kg, i.v.), a selective cyclooxygenase-2 inhibitor, at I h prior to middle cerebral artery occlusion in cortical spreading depression preconditioned animals did not affect infarct volume (162.6 +/- 62.1 mm(3)). However, administration of N-[2-cyclohexyloxy-4-nitrophenyl] methanesulphonamide given three times prior to middle cerebral artery occlusion prevented the reduced infarct volume induced by cortical spreading depression preconditioning (272.9 +/- 63.2 mm(3)). Administration Of L-nitro-arginine methyl ester (4 mg/kd, i.v.) prior to cortical spreading depression blocked increases in cyclooxygenase-2 normally seen at 3 and 4 days. We conclude that NO-mediated cyclooxygenase-2 upregulation by cortical spreading depression protects the brain, against ischemic damage. (c) 2006 Published by Elsevier Ltd on behalf of IBRO.