SPHINGOMYELIN CHANGES IN RAT CEREBRAL-CORTEX DURING FOCAL ISCHEMIA

To better define the sphingolipid metabolism during focal brain ischem ia, levels of ceramide, sphingomyelin, cerebroside and gangliosides we re determined in rat cerebral cortex during focal ischemia produced by occlusion of the middle cerebral artery. Sphingomyelin began to decre ase at 2 hours of ischemia and continued to decrease for 96 hours. In contrast ceramide increased at 6 hours and increased to 4.2-fold at 96 hours after ischemia, and the fatty acid composition of ceramide was solely nonhydroxylated fatty acid similar to sphingomyelin. Hydroxylat ed fatty acid-linked cerebroside decreased at 6 hours of ischemia, whe reas any significant decrease of nonhydroxylated fatty acid-linked cer ebroside didn't occur for 96 hours of ischemia. There were no measurab le changes in the levels of gangliosides. These results suggested that ceramide was produced in the cerebral cortex by the breakdown of sphi ngomyelin during early ischemia.