Evolving possible link between PI3K and NO pathways in neuroprotective mechanism of ischemic postconditioning in mice.

The present study was conducted to pharmacologically investigate the influence of NO signaling pathway in PI3K mediated neuroprotective mechanism of ischemic postconditioning (iPoCo). Bilateral carotid artery occlusion (BCAO) of 12 min followed by reperfusion for 24 h was employed to produce ischemia/reperfusion-induced cerebral injury in male Swiss mice. Memory was assessed using Morris water maze test. Degree of motor incoordination was evaluated using inclined beam walk test, rotarod test, and lateral push test. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Brain acetylcholinesterase activity, thiobarbituric acid reactive species (TBARS), nitrite/nitrate and reduced glutathione (GSH) levels were also estimated. BCAO followed by reperfusion produced significant rise in cerebral infarct size, acetylcholinesterase activity, and TBARS levels along with fall in nitrite/nitrate and GSH 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 incoordination, and altered biochemicals. iPoCo-induced neuroprotective effects were significantly abolished by wortmannin (a selective PI3K inhibitor). However, administration of L-Arginine (a NO precursor) in the presence of wortmannin restored the protective effect of ischemic postconditioning. It may be concluded that neuroprotective mechanism of iPoCo involves PI3K-mediated pathway with NO signaling as an important downstream step.