title: The role of excitatory amino acids in hypothermic injury to mammalian spinal cord neurons.
abstract: Hypothermia has been reported to be beneficial in CNS physical injury and ischemia. We previously reported that posttraumatic cooling to 17 degrees C for 2 h increased survival of mouse spinal cord (SC) neurons subjected to physical injury (dendrite transection) but that cooling below 17 degrees C caused a lethal NMDA receptor-linked stress to both lesioned and uninjured neurons. The present study tested whether cooling below 17 degrees C increases extracellular levels of excitatory amino acids (EAA). SC cultures were placed at 10 degrees C or 37 degrees C. Glutamate (Glu) and aspartate (Asp) levels were higher in the medium of the cooled cultures after 0.5 h (23 +/- 4 nM/microgram vs. 4 +/- 1 nM/microgram and 4 +/- 1 nM/microgram vs. 1 +/- 0 nM/microgram, respectively). The concentration of each EAA then declined and reached a plateau at 2-4 h that was still significantly higher than control levels (p < 0.0001, two-factor ANOVA, three cultures per group). Other amino acids (glycine, asparagine, glutamine, serine) showed an opposite pattern, with higher levels in the 37 degrees C group. Both NMDA and non-NMDA antagonists prevented the lethal cold injury. Survival of SC neurons cooled at 10 degrees C for 2 h and rewarmed for 22 h was 58% +/- 25% in the control group, 94% +/- 5% in the CNQX-treated group, 97% +/- 5% in the DAPV-treated group, and 99% +/- 2% in the group treated with both antagonists [p < 0.0006, one factor ANOVA, five cultures (> 120 neurons) per group]. These results show that death of neurons cooled to 10 degrees C is caused by elevated extracellular Glu and Asp and requires activation of both the NMDA and non-NMDA receptor subtypes.
authors.affiliation: Department of Physiology, Ohio State University, Columbus 43210, USA.
authors.forename: G
authors.initials: G
authors.lastname: Craenen
authors.forename: S
authors.initials: S
authors.lastname: Jeftinija
authors.forename: I
authors.initials: I
authors.lastname: Grants
authors.forename: J H
authors.initials: JH
authors.lastname: Lucas
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D003080:Cold Temperature; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018846:Excitatory Amino Acids / Q000378:metabolism / Q000502:physiology*; D018698:Glutamic Acid / Q000378:metabolism; D051379:Mice / Q000196:embryology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012016:Reference Values; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013119:Spinal Cord Injuries / Q000209:etiology* / Q000473:pathology
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018846:Excitatory Amino Acids; D016194:Receptors, N-Methyl-D-Aspartate; D001224:Aspartic Acid; D018698:Glutamic Acid; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate