Hypoxic postconditioning enhances functional recovery following endothelin-1 induced middle cerebral artery occlusion in conscious rats

Stroke is a leading cause of death and a major contributor to neurological disability in adults. Tissue plasminogen activator is the only approved treatment. However, due to its narrow therapeutic window, <5% of patients receive treatment. Recently, hypoxic postconditioning (HPC) was shown to reduce stroke induced-injury in mice, but the mechanisms and functional outcomes are still unknown. In the current study, male Sprague Dawley rats were subjected to endothelin-1 induced stroke. HPC (8% O2, 1 h/d for 5d) or normoxia treatments were started 24 h after stroke. Behavioural tests were performed at various time-points (pre- and post-surgery, 1 and 6 days post stroke) and brains were collected 6 days after stroke for histological and immunoblotting analysis. HPC improved deficits in neurological score, motor and sensory function after stroke. Furthermore, HPC reduced infarct volume and neuronal loss in the cortex, while it increased the number of astrocytes and of Fluoro-Jade-positive cells in the injured hemisphere. We observed a mild increase in HIF-1 and its target gene, glucose transporter-1. Our data suggest that HPC-induced neuroprotection was mediated by enhanced astrocyte function, which may have contributed to functional recovery after stroke.