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

Abstract

This study reports an online temperature correction method for determining tissue oxygen partial pressure ( P t O 2 ) in the striatum and a novel simultaneous measurement of brain P t O 2 and temperature ( T brain) in conjunction with global oxygen consumption ( V O 2 ) 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 P O 2 in hibernating or other cool-blooded species. P t O 2 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 P t O 2 are different from blood oxygen partial pressure ( P a O 2 ) 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 P O 2 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.