Simultaneous measurement of brain tissue oxygen partial pressure, temperature, and global oxygen consumption during hibernation, arousal, and euthermy in non-sedated and non-anesthetized Arctic ground squirrels

This study reports an online temperature correction method for determining tissue oxygen partial pressure (PtO2)(PtO2) in the striatum and a novel simultaneous measurement of brain PtO2PtO2 and temperature (Tbrain) in conjunction with global oxygen consumption (VO2)(VO2) in non-sedated and non-anesthetized freely moving Arctic ground squirrels (AGS, Spermophilus parryii  ). This method fills an important research gap—the lack of a suitable method for physiologic studies of tissue PO2PO2 in hibernating or other cool-blooded species.PtO2PtO2 in AGS brain during euthermy (21.22 ± 2.06 mmHg) is significantly higher (P = 0.016) than during hibernation (13.21 ± 0.46 mmHg) suggests brain oxygenation in the striatum is normoxic during euthermy and hypoxic during hibernation. These results in PtO2PtO2 are different from blood oxygen partial pressure (PaO2)(PaO2) in AGS, which are significantly lower during euthermy than during hibernation and are actually hypoxic during euthermy and normoxic during hibernation in our previous study. This intriguing difference between the PO2PO2 of brain tissue and blood during these two physiological states suggests that regional mechanisms in the brain play a role in maintaining tissue oxygenation and protect against hypoxia during hibernation.