The Journal of Neuroscience, November 15, 2001, 21(22):8746-8757
Subcellular and Subsynaptic Localization of Presynaptic and
Postsynaptic Kainate Receptor Subunits in the Monkey Striatum
Jeremy Z.
Kieval,
G. W.
Hubert,
Ali
Charara,
Jean-François
Paré, and
Yoland
Smith
Division of Neuroscience, Yerkes Regional Primate Research Center,
and Department of Neurology, Emory University, Atlanta, Georgia 30322
The localization and functions of kainate receptors (KARs) in the
CNS are still poorly known. In the striatum, GluR6/7 and KA2
immunoreactivity is expressed presynaptically in a subpopulation of
glutamatergic terminals and postsynaptically in dendrites and spines.
The goal of this study was to further characterize the subcellular and
subsynaptic localization of kainate receptor subunits in
the monkey striatum. Immunoperoxidase data reveal that the relative
abundance of GluR6/7- and KA2-immunoreactive terminals is homogeneous
throughout the striatum irrespective of the differential degree of
striatal degeneration in Huntington's disease. Pre-embedding and
post-embedding immunogold data indicate that >70% of the presynaptic or postsynaptic GluR6/7 and KA2 labeling is expressed intracellularly. In material stained with the post-embedding immunogold method, approximately one-third of plasma membrane-bound gold
particles labeling in axon terminals and spines is associated with
asymmetric synapses, thereby representing synaptic kainate receptor
subunits. On the other hand, >60% of the plasma-membrane bound
labeling is extrasynaptic. Both GluR6/7 and KA2 labeling in
glutamatergic terminals often occurs in clusters of gold particles
along the membrane of large vesicular organelles located at various
distances from the presynaptic grid. Anterograde labeling from the
primary motor cortex or the centromedian thalamic nucleus indicate that both corticostriatal and thalamostriatal terminals express presynaptic GluR6/7 and KA2 immunoreactivity in the postcommissural putamen. In
conclusion, these data demonstrate that kainate receptors in the
striatum display a pattern of subcellular distribution different from
other ionotropic glutamate receptor subtypes, but consistent with their
metabotropic-like functions recently shown in the hippocampus.
Key words:
Huntington's disease; excitotoxicity; presynaptic
receptor; corticostriatal pathway; thalamostriatal pathway; post-embedding immunogold
Copyright © 2001 Society for Neuroscience 0270-6474/01/21228746-12$05.00/0
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