Fluctuation of Brain Tissue Oxygen Partial Pressure: A Biochemical Landmark in the Arctic Ground Squirrel's Spontaneous Arousal

Abstract

Hibernation in the Arctic Ground Squirrel (AGS) is a regulated, adaptive response to arctic environmental conditions. Problem statement: Regional brain Blood Flow (rCBF) has been observed to increase dramatically during arousal in hibernators. However, the real time dynamic change in P t O 2 during arousal has not been studied, we hypothesized that P t O 2 is Interdependent of T brain and a key component in the arousal process. Approach: Simultaneous in vivo measurements of P t O 2 and brain temperature (T brain ) in conjunction with oxygen consumption (V 02 ) were conducted in the striatum of non-sedated, non-anesthetized Arctic ground squirrels during spontaneous arousal from hibernation. Results: A dramatic fluctuation of brain tissue oxygen partial pressure (P t O 2 ) is associated with the complex phenomena of spontaneous arousal. In this study, we observed that: (1) a P t O 2 elevation precedes changes in T brain and V 02 ; (2) P t O 2 changes do not correlate with changes in V 02 during arousal and (3), endogenous O 2 shift from O 2 enriched blood to brain in hibernating AGS induces an arousal with the pharmaceutical chemical, efaproxiral (RSR-13). Conclusion: The four turning points of P t O 2 appearing at different T brain during arousal suggest that changes in P t O 2 are T brain interdependent and support the concept that arousal from hibernation is complex process invoking different feedbacks.