Prolonged inhibition of glutamate reuptake down-regulates NMDA receptor functions in cultured cerebellar granule cells

J Neurochem. 1999 May;72(5):2181-90. doi: 10.1046/j.1471-4159.1999.0722181.x.

Abstract

In the present study, we have examined the effects of prolonged (up to 72 h) inhibition of high-affinity glutamate reuptake by L-trans-pyrrolidine-2,4-dicarboxylate (PDC; 100 microM) on glutamate receptor functions in primary cultures of rat cerebellar granule neurons. This was done by comparing the effects of various glutamate receptor agonists on neuronal 45Ca2+ uptake, free cytoplasmic Ca2+ concentration ([Ca2+]i), and cell viability. We also determined the parameters of[3H]MK-801 binding as well as the expression of the NMDAR1 subunit protein in control and PDC-exposed cultures. The blockade of glutamate reuptake by PDC led to a gradual increase of ambient glutamate to concentrations that are neurotoxic when applied acutely to control cells. In PDC-exposed cells, however, the acute glutamate-induced NMDA receptor-mediated calcium fluxes were strongly diminished and no toxicity was observed. The down-regulation of the functional effects of glutamate was dependent on the duration of PDC exposure and was accompanied by a reduced NMDAR1 subunit expression and decreased [3H]MK-801 binding, indicative of a pronounced structural rearrangement of NMDA receptors. The possibility that the decrease of NMDA glutamate receptor sensitivity can be explained on the basis of a reduced density or altered subunit composition of NMDA receptors is discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism
  • Calcium / pharmacokinetics
  • Cells, Cultured
  • Cerebellum / cytology
  • Cerebellum / metabolism*
  • Cytoplasm / metabolism
  • DNA Fragmentation
  • Dicarboxylic Acids / pharmacology
  • Dizocilpine Maleate / metabolism
  • Down-Regulation / physiology*
  • Enzyme-Linked Immunosorbent Assay
  • Excitatory Amino Acid Antagonists*
  • Glutamates / metabolism
  • Histones / genetics
  • Neurons / metabolism
  • Neurotoxins / metabolism
  • Neurotransmitter Uptake Inhibitors / pharmacology
  • Pyrrolidines / pharmacology
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, N-Methyl-D-Aspartate / metabolism*
  • Time Factors

Substances

  • Dicarboxylic Acids
  • Excitatory Amino Acid Antagonists
  • Glutamates
  • Histones
  • Neurotoxins
  • Neurotransmitter Uptake Inhibitors
  • Pyrrolidines
  • Receptors, N-Methyl-D-Aspartate
  • Dizocilpine Maleate
  • pyrrolidine-2,4-dicarboxylic acid
  • Calcium