Brain antioxidant levels in hamsters during hibernation, arousal and cenothermia

Warming from hibernation to cenothermia involves intense metabolic activity coincident with large fluxes in blood flow and is considered to be a period of oxidative stress during which utilization of endogenous antioxidants prevents pathology. Very slow flow brain microdialysis enabled temperature independent sampling of the brain striatal extracellular fluid (ECF) during hibernation, arousal and cenothermia in Syrian hamsters (Mesocricetus auratus). Brain tissue and dialysates were analyzed to provide the first profile of changes in ECF levels of ascorbate (AA), glutathione (GSH) and urate during hibernation and the transition to cenothermia. Brain tissue content of AA and GSH was unchanged between hibernation and cenothermia; however, arousal was associated with substantial oxidation of AA from the brain ECF and plasma compartments. ECF GSH increased during arousal. Brain tissue urate content was decreased 50% during hibernation. ECF urate levels were unchanged in hibernation and cenothermia but transiently increased 100% during arousal. These experiments demonstrate that arousal from hibernation is a suitable experimental model for examination of the mechanisms by which non-pathological tissue integrity is maintained in the face of the generation of free radicals during increasing metabolism, temperature and cerebral reperfusion.