The effects of hibernation on the chemical composition of cerebrospinal and intraocular fluids, blood plasma and brain tissue of the woodchuck ( Marmota monax)

Abstract

1. 1. Blood plasma and ocular (IOFs) and cerebrospinal fluids (CSFs) from hibernating and nonhibernating (anaesthetized) woodchucks were assayed for the following constituents: Na +, K +, Mg 2+, Ca 2+, glucose, lactate, ascorbate, total α-amino N, glutamine, glutamate and protein concentrations and total osmolarity. Water and electrolyte content of brain gray and white matter were also determined. 2. 2. During hibernation, the [Mg 2+] of plasma and CSFs, but not of IOFs, was greatly elevated; [glucose] and [lactate] were significantly lowered, while [ascorbate] was maintained at a concentration well above that of plasma. 3. Plasma [K +] of hibernating woodchucks was similar to that of active (excited) animals but significantly higher than that of resting or anaesthetized normothermic animals. [K +] of cortical subarachnoid fluid was nearly doubled in the early phase of hibernation, but that of other fluids remained essentially normal. 3. 4. Brain [K +] and [Mg 2+] were significantly decreased in hibernation without a concomitant increase in [Na +]. 4. 5. It is concluded that active transport of some solutes across the blood-brain and blood-ocular barriers continues during hibernation. 5. 6. The effects of hibernation on brain electrolytes are not consistent with a cold-induced Na-K shift, but are consistent with the possiblility that the cerebral cortex undergoes physiological changes in hibernation similar to those thought to occur in acute cortical shutdown.