Changes in the contents of glycogen and lactate in the brain and blood during hypoxic preconditioning.

Mice were randomly divided into groups H4 (hypoxic preconditioning group with repetitive hypoxic exposures for four runs), H(1) (hypoxic control group with exposure to hypoxia for one run) and H(0) (normal control group with no exposure to hypoxia). Glycogen content of whole brain of group H4 was found to be significantly higher than that of groups H(1) and H(0). The glycogen content in telencephalon, diencephalon and pons of group H4 was markedly higher than that in the corresponding areas of groups H(1) and H(0). Glycogen content of whole brain in group H(1) was markedly lower than that in group H(0), whereas no significant difference was seen in these brain subregions between groups H(1) and H(0). Brain lactate contents of groups H4 and H(1) did not show significant difference, though they were significantly higher than that of group H(0). Blood lactate content of group H4 was significantly lower than those of groups H(1) and H(0). The results above indicate that the concomitant increase of glycogen and decrease of lactate in the brain are due to the participation of aerobic metabolism during hypoxic preconditioning or the formation of tolerance to hypoxia.