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Elevated Cortical Extracellular Fluid Glutamate in Transgenic Mice Expressing Human Mutant (G93A) Cu/Zn Superoxide Dismutase
Author(s) -
Alexander Guillermo M.,
Deitch Jeffrey S.,
Seeburger Jeffrey L.,
Valle Luis Del,
HeimanPatterson Terry D.
Publication year - 2000
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2000.0741666.x
Subject(s) - glutamate receptor , glutamate aspartate transporter , sod1 , microdialysis , extracellular , biology , superoxide dismutase , biochemistry , glutamic acid , chemistry , microbiology and biotechnology , metabotropic glutamate receptor , amino acid , oxidative stress , receptor
Transgenic mice expressing a mutated (G93A) human Cu/Znsuperoxide dismutase (SOD1) develop motor neuron pathology and clinicalsymptoms similar to those seen in patients with amyotrophic lateral sclerosis.Loss of motor neurons is most prominent in lumbar, followed by cervical cordand then brainstem. No significant cell death has been reported in motorcortex. The integrity of the cortical glutamate reuptake systems was evaluatedusing intracerebral microdialysis and western immunoblot assays for theglutamate transporters GLT‐1, GLAST, and EAAC1. The basal extracellular fluidlevels of aspartate, glutamate, glutamine, 3,4‐dihydroxyphenylacetic acid, and5‐hydroxyindole‐3‐acetic acid were evaluated by HPLC. The extraction fractionof L‐[ 3 H]glutamate, corrected with [ 14 C]mannitol, wasalso evaluated. GLT‐1, EAAC1, and GLAST protein levels were determined bysemiquantitative chemiluminescence immunoblot of proteins frommembrane‐enriched fractions. The relative optical density of film wastranslated into relative protein level by comparison with a standard controlmouse. The SOD1 mutant mice demonstrated a significant ( p < 0.05)increase in basal levels of extracellular aspartate and glutamate. Inaddition, when the glutamate extraction fraction was challenged with exogenousunlabeled glutamate (500 μ M ) by reversed microdialysis, the glutamate extraction fraction in the mutant SOD1 mice was decreased significantly from control levels. The SOD1 mutant mice demonstrated no difference in the cortical protein levels of the glutamate transporter subtypes. This study demonstrates that in areas of no visible pathology and no loss of glutamate transporter proteins, SOD1 mutant mice have elevated extracellular fluid aspartate and glutamate levels and a decreased capacity to clear glutamate from the extracellular space.