Relationship between Preconditioning with Intermittent Hyperoxia on Na/Ca2+ Exchanger 1 Level and Brain Infarct Volume in Rat Stroke Model

Inroduction & Recent studies suggest that Normobaric Hyperoxia (HO) decreases hypoxia-reoxygenation injury, increases expression of Na/Ca2+ Exchanger1 (NCX1) in brain. We wanted to determine the relationship between HO effects on NCX1 and infarct volume (IV) in rat stroke model. Rats were divided into two experimental groups. The first group was exposed to 95% inspired HO for 4 hours/day for 6 consecutive days (HO). The second group acted as control and was exposed to 21% oxygen in the same chamber. Each main group was sub-divided to middle cerebral artery occlusion (MCAO-operated) and intact (without any surgery) sub-groups. After 2, 5, 10 and 15 days from pre-treatment, MCAO-operated sub-groups were subjected to 60 minutes of right MCAO. After 24 hours reperfusion, infarct volume was measured in MCAO-operated sub-groups. The NCX1 expression levels of core, penumbra and sub-cortex regions were assessed in sham-operated and intact sub-groups. Pre-conditioning with HO decreased infarct volume, and increased expression of NCX1 in penumbra and sub-cortex. These effects of hyperoxia disappeared gradually during 15 days after pre-treatment. Although further studies are needed to clarify the mechanisms of time course of neuroprotection, HO partly is associated with expression of NCX1 consistent with an active role in the genesis of ischaemic neuroprotection.