Abstract
During arousal from hibernation, as body temperature increases by about 20-30 °C toward cenothermia within 1 hr, hamster brain is exposed to an intense oxidation stress. We measured ascorbic acid (AA), reduced glutathione (GSH) and uric acid (UA) in the brain tissue homogenate and brain extracellular fluid (ECF) by using very slow flow (3.5 μL/h) microdialysis technique and HPLC to investigate the interaction between water-soluble antioxidants along the time course of arousal from hibernation. Microdialysis probe was located at unilateral striatum, and perfused with artificial cerebrospinal fluid (aCSF) or aCSF containing 60 μM oxypurinol, a xanthine dehydrogenase/oxidase (XOR) inhibitor. Glucose lacking perfusate had no effect upon the respective decrease, increase and transient increase in ECF levels of AA, GSH and UA observed during arousal from hibernation to cenothermia. Inhibition of XOR activity by reverse dialysis with oxypurinol, itself a free radical scavenger, decreased ECF UA and preserved AA levels in the ECF. GSH level was not affected by this treatment with XOR inhibitor. Local supplementation of ECF antioxidants (AA, GSH and cysteine) had no effect upon the profile of transient increase of ECF UA observed during arousal from hibernation. Free radical production by XOR and disappearance of AA from the ECF continues for at least 2 h after the hamster has attained cenothermia. Results suggest that AA is oxidized by free radical of XOR products and/or by other free radical producing processes activated during the arousing phase of hibernation. [J Physiol Sci. 2007;57 Suppl:S179]
