During the pre-hibernation season, arctic ground squirrels (AGS) can tolerate 8 min of asphyxial cardiac arrest (CA) without detectable brain pathology. Better understanding of the mechanisms regulating innate ischemia tolerance in AGS has the potential to facilitate the development of novel prophylactic agents to induce ischemic tolerance in patients at risk of stroke or CA. We hypothesized that neuroprotection in AGS involves robust maintenance of ion homeostasis similar to anoxiatolerant turtles. Ion homeostasis was assessed by monitoring ischemic depolarization (ID) in cerebral cortex during CA in vivo and during oxygen glucose deprivation in vitro in acutely prepared hippocampal slices. In both models, the onset of ID was significantly delayed in AGS compared with rats. The epsilon protein kinase C (ePKC) is a key mediator of neuroprotection and inhibits both Na + /K + -ATPase and voltage-gated sodium channels, primary mediators of the collapse of ion homeostasis during ischemia. The selective peptide inhibitor of ePKC (eV1-2) shortened the time to ID in brain slices from AGS but not in rats despite evidence that eV1-2 decreased activation of ePKC in brain slices from both rats and AGS. These results support the hypothesis that ePKC activation delays the collapse of ion homeostasis during ischemia in AGS.

Vessel painting is a simple, cost-effective way to visualize the vascular architecture of the mouse brain and other organs. DiI is a lipophilic carbocyanine dye that binds to lipid membranes and is commonly used for tract tracing in the brain. After perfusion with PBS to remove the blood, perfusion with a special DiI solution allows direct staining of the vasculature. This step is followed by perfusion fixation and removal of the brain from the skull. Pial vessels can be directly imaged using a standard fluorescent microscope. To acquire images of the whole brain, a montage of images at different focal planes is assembled. Basic cerebral vascular anatomy is reviewed in the context of vessel painting, and examples are presented showing enhanced collateralization in a mouse model of metabolic syndrome. Vessel painting offers a cost-effective and efficient alternative to more complex approaches such as corrosion casting.