Delayed treatment with carboxy-ptio permits a 4-h therapeutic window of opportunity and prevents against ischemia-induced energy depletion following permanent focal cerebral ischemia in mice

We examined whether a nitric oxide scavenger, 2-(4-carboxyphenyl)-4,4,5,5- tetramethyl-imidazoline-l-oxyl-3-oxide (carboxy-PTIO), could offer neuroprotective actions and improve cerebral energy metabolism in a model of stroke. Sixty C57BL/10J mice were given either carboxy-PTIO (0.3-1.2 mg/kg) or vehicle intraperitoneally, 0.5 h after permanent middle cerebral artery occlusion, to evaluate the dose-response effects. An additional 70 animals received carboxy-PTIO (0.6 mg/kg) or vehicle, 2-6 h post-ischemia, for establishing the therapeutic window. Subgroups of animals, treated with carboxy-PTIO (0.6 mg/kg) or vehicle, were used for measuring cerebral bioenergetic metabolites (ATP, ADP, AMP, adenosine). Mice treated with carboxy-PTIO (0.6 mg/kg) had dose-specifically reduced brain infarction, significantly by 27-30% (P < 0.05), even when therapy was delayed up to 4 h after the ischemic insult (P < 0.05). Four hour post-ischemia, ATP depleted in the ischemic hemisphere (P < 0.05). Administration with carboxy-PTIO not only improved the recovery of ATP in the ischemic hemisphere (P < 0.05), but also enhanced adenosine content across the ischemic and non-ischemic hemispheres (P < 0.05). The neuroprotection of carboxy-PTIO may be partly attributed to the beneficial effects of improving cerebral energy metabolism.