Nitric oxide synthase inhibitor is an effective therapy for ischemia‐reperfusion injury in mice

Inhibition of nitric oxide synthase (NOS) has been shown to paradoxically protect against ischemic brain injury by an unknown mechanism. Recently, we found that NOS inhibitor, N (gamma)-nitro-L-arginine methyl ester (L-NAME), protects primary cultures of endothelial cells and neurons against oxygen-glucose deprivation-reoxygenation injury by preventing NOS uncoupling. Thus, the objective of the present study was to demonstrate the effectiveness of locally administered L-NAME against ischemia-reperfusion (I-R) injury.Transient focal cerebral ischemia in male mice (C57Bl/6, 2-4 months) was achieved by filament method of MCAO with a 60 min occlusion. We employed a novel approach to inject L-NAME (1 mg/Kg dosages at a rate of 60 ug/minute) locally into the ischemic zone by threading a catheter up the middle cerebral artery. This was timed to the onset of reperfusion by rapidly followng the removal of the occlusion with the silicon suture. Following 24-hour reperfusion, infarct size was determined by 2,3,5-Triphenyltetrazolium chloride (TTC) staining and neurological function was assessed by employing a standard neurological score (0-4 range) and Rotarod performance test.Admnistration of FITC Dextran 40K and fluorescence microscopy of the brain slices 1 hour post-ischemia confirmed the effective delivery of injected L-NAME into the ischemic tissue. Localized injection of L-NAME was protective against I-R injury and promoted significant recovery of neurological and motor function (Figure).Local NOS inhibition could serve as an adjuvant for reperfusion therapies of ischemic stroke.