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 (P-tO2) in the striatum and a novel simultaneous measurement of brain P-tO2 and temperature (T-brain) in conjunction with global oxygen consumption (V-O2) 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-O2, in hibernating or other cool-blooded species. P-tO2 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-tO2 are different from blood oxygen partial pressure (P-aO2) 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-O2 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. (C) 2008 Elsevier B.V. All rights reserved.