Modulation of glutamate transport and receptor binding by glutamate receptor antagonists in EAE rat brain

PLoS One. 2014 Nov 26;9(11):e113954. doi: 10.1371/journal.pone.0113954. eCollection 2014.

Abstract

The etiology of multiple sclerosis (MS) is currently unknown. However, one potential mechanism involved in the disease may be excitotoxicity. The elevation of glutamate in cerebrospinal fluid, as well as changes in the expression of glutamate receptors (iGluRs and mGluRs) and excitatory amino acid transporters (EAATs), have been observed in the brains of MS patients and animals subjected to experimental autoimmune encephalomyelitis (EAE), which is the predominant animal model used to investigate the pathophysiology of MS. In the present paper, the effects of glutamatergic receptor antagonists, including amantadine, memantine, LY 367583, and MPEP, on glutamate transport, the expression of mRNA of glutamate transporters (EAATs), the kinetic parameters of ligand binding to N-methyl-D-aspartate (NMDA) receptors, and the morphology of nerve endings in EAE rat brains were investigated. The extracellular level of glutamate in the brain is primarily regulated by astrocytic glutamate transporter 1 (GLT-1) and glutamate-aspartate transporter (GLAST). Excess glutamate is taken up from the synaptic space and metabolized by astrocytes. Thus, the extracellular level of glutamate decreases, which protects neurons from excitotoxicity. Our investigations showed changes in the expression of EAAT mRNA, glutamate transport (uptake and release) by synaptosomal and glial plasmalemmal vesicle fractions, and ligand binding to NMDA receptors; these effects were partially reversed after the treatment of EAE rats with the NMDA antagonists amantadine and memantine. The antagonists of group I metabotropic glutamate receptors (mGluRs), including LY 367385 and MPEP, did not exert any effect on the examined parameters. These results suggest that disturbances in these mechanisms may play a role in the processes associated with glutamate excitotoxicity and the progressive brain damage in EAE.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / drug effects*
  • Brain / metabolism*
  • Encephalomyelitis, Autoimmune, Experimental / drug therapy
  • Encephalomyelitis, Autoimmune, Experimental / metabolism*
  • Excitatory Amino Acid Antagonists / pharmacology*
  • Excitatory Amino Acid Transporter 1 / metabolism
  • Excitatory Amino Acid Transporter 2 / metabolism
  • Female
  • Glutamic Acid / analysis
  • Glutamic Acid / metabolism*
  • Rats
  • Rats, Inbred Lew
  • Receptors, Glutamate / metabolism
  • Receptors, N-Methyl-D-Aspartate / metabolism

Substances

  • Excitatory Amino Acid Antagonists
  • Excitatory Amino Acid Transporter 1
  • Excitatory Amino Acid Transporter 2
  • Receptors, Glutamate
  • Receptors, N-Methyl-D-Aspartate
  • Slc1a2 protein, rat
  • Glutamic Acid

Grants and funding

This study was supported by grant nr NN 401620038 from the Polish Ministry of Science and Higher Education. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.