Cellular, Subcellular, and Subsynaptic Distribution of AMPA-Type Glutamate Receptor Subunits in the Neostriatum of the Rat

Abstract

Glutamate released in the basal ganglia is involved in the expression of clinical symptoms of neurodegenerative diseases like Parkinson's or Huntington's. Neostriatal neurons are the targets of glutamatergic inputs derived from the cortex and the thalamus acting via AMPA-type as well as other glutamate receptors. To determine the location of subunits of the AMPA subclass of glutamate receptors (GluR) in the rat neostriatum, we applied multiple immunocytochemical techniques using anti-peptide antibodies against the GluR1, GluR2/3, and GluR4 subunits at both the light and electron microscopic levels. All medium spiny efferent neurons, some of which were identified as striatonigral neurons, displayed immunoreactivity for GluR1 and GluR2/3 subunits. Double immunofluorescence revealed that at least 70-90% of parvalbumin-immunopositive GABAergic interneurons were immunoreactive for each of GluR1, GluR2/3, or GluR4 subunits and that at least 40% of choline acetyltransferase-immunopositive cholinergic interneurons were immunopositive for GluR1 or GluR4 subunits. The majority of nitric oxide synthase-immunopositive neurons had no detectable immunoreactivity for any of the AMPA receptor subunits. Electron microscopic analysis confirmed the presence of immunoreactivity for GluR1 and GluR2/3 in the perikarya of spiny neurons and interneurons and GluR4 in perikarya of interneurons only. GluR1 and GluR2/3 subunits were detected in dendrites and spines. A significant population of extrasynaptic receptors was revealed by pre-embedding immunogold labeling along the plasma membranes of perikarya, dendrites, and spines. Receptors were concentrated in the postsynaptic membrane specialization of asymmetrical synapses, as revealed by the postembedding immunogold method. Quantitative analysis demonstrated that immunoreactivity for the GluR1 and GluR2/3 subunits is higher at the periphery than at the middle of the postsynaptic membrane specialization. Our results demonstrate that AMPA receptor subunits are distributed widely and heterogeneously among striatal neurons and are concentrated on the postsynaptic membrane of asymmetrical synaptic specializations, although extrasynaptic receptors are also present.

Subcellular and Subsynaptic Localization of Presynaptic and Postsynaptic Kainate Receptor Subunits in the Monkey Striatum

“…Furthermore, it has been shown that the presynaptic control of GABA release by kainate receptors in the hippocampus is mediated by a metabotropic process that is sensitive to Pertussis toxin and independent of ion channel current (Rodriguez-Moreno and Lerma, 1998). These functional data combined with results of our study clearly indicate that both the localization and functions of kainate receptors are strikingly different from those of conventional ionotropic glutamate receptors that are largely confined to the main bodies of synaptic active zones (Bernard et al, 1997;Ottersen and Landsend, 1997) and mediate fast synaptic transmission. It is noteworthy that a substantial level of intracellular AMPA glutamate receptor subunits immunoreactivity has recently been found in dendrites of dorsal cochlear neurons in rats (Rubio and Wenthold, 1999).…”

Synaptic AMPA receptor composition in development, plasticity and disease

“…GluA4, on the other hand is tightly developmentally regulated and is sparsely expressed at glutamatergic synapses in principal neurons in adult brain 12 . It should be noted, however, that GluA4 is a key determinant of the properties of AMPAR-mediated transmission in interneurons, especially in parvalbumin-containing inhibitory interneurons 13,14 .…”

“…GluA4, on the other hand is tightly developmentally regulated and is sparsely expressed at glutamatergic synapses in principal neurons in adult brain 12 . It should be noted, however, that GluA4 is a key determinant of the properties of AMPAR-mediated transmission in interneurons, especially in parvalbumin-containing inhibitory interneurons 13,14 .Research over the last 20 years has resulted in the prevailing view that a canonical hierarchy of subunit-specific rules coordinates the properties and trafficking of AMPARs, in a manner dependent on their intracellular C-termini. GluA1 is dominant in activity-dependent recruitment of AMPARs to synapses.…”

Molecular Cloning and Characterization of Phocein, a Protein Found from the Golgi Complex to Dendritic Spines

“…The brain and adrenal glands were removed and postfixed in the same solution. Vibratome sections, 30 -40 m, were cut and processed for immunocytochemistry at the optical level, using the immunoperoxidase method as described previously (Bernard et al, 1997). Briefly, sections were preincubated in PBS containing 10% normal goat serum and incubated for 15 h at room temperature in a solution containing the primary antibodies.…”