Real-time imaging of glutamate clearance reveals normal striatal uptake in Huntington disease mouse models

Nat Commun. 2016 Apr 7:7:11251. doi: 10.1038/ncomms11251.

Abstract

It has become well accepted that Huntington disease (HD) is associated with impaired glutamate uptake, resulting in a prolonged time-course of extracellular glutamate that contributes to excitotoxicity. However, the data supporting this view come largely from work in synaptosomes, which may overrepresent nerve-terminal uptake over astrocytic uptake. Here, we quantify real-time glutamate dynamics in HD mouse models by high-speed imaging of an intensity-based glutamate-sensing fluorescent reporter (iGluSnFR) and electrophysiological recordings of synaptically activated transporter currents in astrocytes. These techniques reveal a disconnect between the results obtained in synaptosomes and those in situ. Exogenous glutamate uptake is impaired in synaptosomes, whereas real-time measures of glutamate clearance in the HD striatum are normal or even accelerated, particularly in the aggressive R6/2 model. Our results highlight the importance of quantifying glutamate dynamics under endogenous release conditions, and suggest that the widely cited uptake impairment in HD does not contribute to pathogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Astrocytes / metabolism*
  • Astrocytes / pathology
  • Biological Transport
  • Corpus Striatum / metabolism*
  • Corpus Striatum / pathology
  • Dependovirus / genetics
  • Disease Models, Animal
  • Genes, Reporter
  • Genetic Vectors
  • Glutamic Acid / metabolism*
  • Humans
  • Huntington Disease / metabolism*
  • Huntington Disease / pathology
  • Male
  • Membrane Potentials / physiology
  • Mice
  • Mice, Transgenic
  • Optical Imaging / methods*
  • Synapses / metabolism*
  • Synaptosomes / metabolism

Substances

  • Glutamic Acid