Effects of Melatonin on Content of NO and Activity of NOS after Focal Cerebral Ischemia in Rats and its Mechanism

Objective To explore the protective effects and mechanism of melatonin on permanent focal cerebral ischemia.Methods Brain ischemia was caused by right middle cerebral artey occlusion(MCAO) for 30 min,6h and 24h respectively in rats.Brain damage was measured by content of NO and activity of NOS.Results The activity of NOS and the content of NO increased at 30 min after cerebral ischemin,and then at 6h decreased, but at 24h increased again.Melatonin significantly elevated activity of NOS and content of NO in 30 min after cerebral ischemia and decreased them at 6h and 24h.Conclusion Melatonin obviously attenuated ischemic brain injury by MCAO,elevated the activity of NOS and content of NO in primitive ischemia and inhibited them in the second time,indicating that the protective effect of melatonin was associated with the debasement of NO-content and NOS-activity and the antagonism to peroxyl radical.