Extracellular Glutamate Levels Are Chronically Elevated in the Brains of LP-BM5-Infected Mice: A Mechanism of Retrovirus-Induced Encephalopathy
Version of Record online: 13 NOV 2002
Journal of Neurochemistry
Volume 71, Issue 5, pages 2079–2087, November 1998
How to Cite
Espey, M. G., Kustova, Y., Sei, Y. and Basile, A. S. (1998), Extracellular Glutamate Levels Are Chronically Elevated in the Brains of LP-BM5-Infected Mice: A Mechanism of Retrovirus-Induced Encephalopathy. Journal of Neurochemistry, 71: 2079–2087. doi: 10.1046/j.1471-4159.1998.71052079.x
- Issue online: 13 NOV 2002
- Version of Record online: 13 NOV 2002
- Received March 25, 1998; revised manuscript received May 13, 1998; accepted May 15, 1998.
- Glutamine synthetase;
- Cerebrospinal fluid;
- AIDS dementia complex
Abstract: Mice infected with the LP-BM5 leukemia retrovirus mixture develop a progressive immunodeficiency with associated behavioral, histological, and neurochemical alterations consistent with glutamatergic hyperactivation. To gain insight into the contribution of excitatory amino acids to the neurodegeneration observed in these mice, their concentrations were measured in the CSF and striatal microdialysates. Glutamate concentrations were significantly elevated in CSF but not plasma as early as 4 weeks postinoculation. Steady-state glutamate levels in striatal microdialysates were increased threefold and could be reduced 40% by application of l-α-aminoadipate, an inhibitor of microglial glutamate transport. Stimulation of infected mice with KCl/l-trans-2,4-pyrrolidine dicarboxylate further increased glutamate levels 170–270% above those evoked in control mice. Tetrodotoxin suppressed the depolarization-evoked increase in glutamate by 88% in control mice, but it had only negligible effects in 40% of infected mice. Analysis of glutamate transport and catabolism suggests that abnormal astrocytic function does not contribute to the increase in basal extracellular glutamate levels. These findings are the first direct evidence that infection with an immunodeficiency-inducing retrovirus leads to a chronic elevation of extracellular free glutamate levels in the brain, which contributes to the neurodegenerative and cognitive deficits observed in these mice.