Pharmacologic evidence for role of endothelial nitric oxide synthase in neuroprotective mechanism of ischemic postconditioning in mice

BackgroundThe present study was conducted to pharmacologically investigate the isoform-specific role of nitric oxide pathway in neuroprotective mechanism of ischemic postconditioning (iPoCo).Materials and methodsBilateral carotid artery occlusion of 12 min followed by reperfusion for 24 h was used to produce ischemia- and reperfusion-induced cerebral injury in male Swiss mice. Memory was assessed using Morris water maze test. Degree of motor in-coordination was evaluated using inclined beam-walk test, rotarod test, and lateral push test. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Brain acetylcholinestrase activity, thiobarbituric acid–reactive species, nitrite/nitrate, and reduced glutathione levels were also estimated. Western blotting was performed to determine endothelial nitric oxide synthase (eNOS) expression.ResultsBilateral carotid artery occlusion followed by reperfusion produced significant rise in cerebral infarct size, acetylcholinesterase activity, and thiobarbituric acid–reactive species levels along with fall in nitrite/nitrate, and glutathione and eNOS expression levels. A significant impairment of memory and motor coordination was also noted. iPoCo consisting of three episodes of 10-s carotid artery occlusion and reperfusion significantly attenuated infarct size, memory impairment, motor in-coordination, altered biochemicals, and protein expression levels. iPoCo-induced neuroprotective effects were significantly abolished by l-NAME (a nonselective nitric oxide synthase inhibitor) and l-NIO (a selective eNOS inhibitor). However, aminoguanidine (a selective inducible nitric oxide synthase inhibitor) and 7-nitroindazole (a selective neuronal nitric oxide synthase inhibitor) did not modulate beneficial effects of iPoCo.ConclusionsIt may be concluded that nitric oxide pathway probably plays a vital role with specific involvement of eNOS in neuroprotective mechanism of iPoCo.