Differential expression of vesicular glutamate transporter 2 in thalamostriatal terminals Pubblico

Abstract

Glutamate is the main excitatory neurotransmitter in the central nervous system, and its transmission is crucial for regulating cognitive functions such as learning and memory. Glutamate transporters help maintain the homeostasis of the glutamatergic system, and vesicular glutamate transporter 2 (vGluT2) in particular is known to be a marker of thalamostriatal projections in the brain. It is unclear, however, as to whether or not the striatum expresses vGluT2-positive as well as vGluT2-negative thalamostriatal projections. This study sought to better understand the expression of vGlut2 in the thalamostriatal system. The anterograde axonal tracer Phaseolus vulgaris-leucoagglutinin (PHA-L) was used to trace projections in 10 adult Sprague Dawley rats from the central medial (CeM) and the parafascicular (Pf) nuclei of the thalamus to the striatum, and immunogold labeling was also used to localize vGluT2 in the striatal tissue. After double-labeling, the striatal tissue was processed and examined with electron microscopy and confocal light microscopy. Anterogradely-labeled terminals from the CeM and the Pf were categorized as PHA-L/vGluT2-positive or PHA-L/vGluT2-negative, and the proportion of vGluT2-immunoreactivity from the CeM and the Pf was quantified to better understand the expression of vGluT2 in the thalamostriatal system. An average of 39.3% (± 4.98%) from the CeM and 47.0% (± 7.55%) from the Pf of the anterogradely-labeled thalamostriatal terminals expressed no vGluT2-immunoreactivity at the EM level. At the confocal microscopic level, an average of 86.7% (± 1.61%) from the CeM and 72.6% (± 3.84%) of the terminals from the Pf were vGluT2-negative. These results suggest that there is a subpopulation of thalamostriatal neurons that do not express vGluT2 and that the thalamostriatal system may give rise to both vGluT2-positive and vGluT2-negative terminals.

Table of Contents

Introduction (1)

History of vGluTs (1)

The Dual Thalamostriatal System (3)

Materials and Methods (6)

Animals and tissue preparation (6)

Immunoperoxidase labeling for electron microscopy (6)

Immunofluorescent staining for light microscopy (9)

Analysis of material (9)

Electron microscopic material (9)

Confocal microscopic material (10)

Results (11)

Discussion (12)

Technical considerations (13)

Future directions (15)

Conclusion (16)

Tables and Figures (17)

Figure 1 - vGluT1 and 2 as markers of thalamostriatal and corticostriatal projections (17)

Figure 2 - Electron micrographs from the CeM and the Pf (18)

Figure 3 - Confocal light microscopic images with ImageJ (19)

Figure 4 - PHA-L injection sites in the Pf and the CeM (20)

Figure 5 - vGluT2 in thalamostriatal projections (electron microscopy) (21)

Figure 6 - vGluT2 in thalamostriatal projections (confocal light microscopy) (22)

References (23)

About this Honors Thesis

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School	Emory College
Department	Neuroscience and Behavioral Biology
Degree	BS
Submission	Honors Thesis
Language	English
Research Field	Biology, Neuroscience
Parola chiave	vesicular glutamate transporter striatum glutamate thalamus
Committee Chair / Thesis Advisor	Smith, Yoland, Emory University
Committee Members	Hall, Randy A, Emory University Roesch, Leah Anderson, Emory University

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