title: The role of glycogen, glucose and lactate in neuronal activity during hypoxia in the hooded seal (Cystophora cristata) brain.
abstract: The brains of diving mammals are repeatedly exposed to hypoxic conditions during diving. Brain neurons of the hooded seal (Cystophora cristata) have been shown to be more hypoxia tolerant than those of mice, but the underlying mechanisms are not clear. Here we investigated the roles of different metabolic substrates for maintenance of neuronal activity and integrity, by comparing the in vitro spontaneous neuronal activity of brain slices from layer V of the visual cortex of hooded seals with those in mice (Mus musculus). Studies were conducted by manipulating the composition of the artificial cerebrospinal fluid (aCSF), containing either 10 mM glucose, or 20 mM lactate, or no external carbohydrate supply (aglycemia). Normoxic, hypoxic and ischemic conditions were applied. The lack of glucose or the application of lactate in the aCSF containing no glucose had little effect on the neuronal activity of seal neurons in either normoxia or hypoxia, while neurons from mice survived in hypoxia only few minutes regardless of the composition of the aCSF. We propose that seal neurons have higher intrinsic energy stores. Indeed, we found about three times higher glycogen stores in the seal brain (∼4.1 ng per μg total protein in the seal cerebrum) than in the mouse brain. Notably, in aCSF containing no glucose, seal neurons can tolerate 20 mM lactate while in mouse neuronal activity vanished after few minutes even in normoxia. This can be considered as an adaptation to long dives, during which lactate accumulates in the blood.
authors: Institute of Zoology and Zoological Museum, Biocenter Grindel, University of Hamburg, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany.
authors: N U
authors: NU
authors: Czech-Damal
authors: Department of Arctic and Marine Biology, University of Tromsø - The Arctic University of Norway, NO-9037 Tromsø, Norway.
authors: S J
authors: SJ
authors: Geiseler
authors: Institute of Zoology and Zoological Museum, Biocenter Grindel, University of Hamburg, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany.
authors: M L M
authors: ML
authors: Hoff
authors: Institute of Zoology and Zoological Museum, Biocenter Grindel, University of Hamburg, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany.
authors: R
authors: R
authors: Schliep
authors: Department of Neurological Surgery, Seattle Children's Research Institute Center for Integrative Brain Research, University of Washington, Seattle, WA, USA.
authors: J-M
authors: JM
authors: Ramirez
authors: Department of Arctic and Marine Biology, University of Tromsø - The Arctic University of Norway, NO-9037 Tromsø, Norway.
authors: L P
authors: LP
authors: Folkow
authors: Institute of Zoology and Zoological Museum, Biocenter Grindel, University of Hamburg, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany. Electronic address: thorsten.burmester@uni-hamburg.de.
authors: T
authors: T
authors: Burmester
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001921:Brain / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology; D004594:Electrophysiology; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism*; D002534:Hypoxia, Brain / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000378:metabolism; D009924:Organ Culture Techniques; D060888:Real-Time Polymerase Chain Reaction; D046048:Seals, Earless / Q000378:metabolism*
chemical_list: D019344:Lactic Acid; D006003:Glycogen; D005947:Glucose
keywords: astrocyte–neuron lactate shuttle; brain; glycogen; hypoxia; ischemia; lactate