Role of N-methyl-D-aspartat receptor-nitric oxide-cyclic guanosin monophosphate pathway in ischemic brain injury

OBJECTIVE: To observe the role of NMDA receptor-Nitric Oxide(NOS)-cGMP pathway in ischemic brain injury. METHODS: The common cervical arteries of the rats were transient blocked bilaterally, in association with bleeding from their tails and followed by reperfusion. The procedures were repeated once again as above to establish a stable ischemic brain injury model. 3H-MK801 binding, cNOS activity, iNOS activity, and the cGMP content were measured at different time intervals after ischemic injury. RESULTS: The results indicated that the change of 3H-MK801 binding varied among the cerebral cortex and hippocampus. cNOS activity began to rise in all parts of the brain 24 hours after operation and reached its peak in 3 days. The regions where iNOS and cNOS activity and cGMP content all increased significantly include the hippocamus, striatum and cortex, especially in hippocampus. CONCLUSIONS: The tendency and degree of increase of those four indixes were cosistent during ischemic injury, indicating an important role of NMDA receptor-NO-cGMP in ischemic injury of the hippocampus.