title: Differential synaptology of vGluT2-containing thalamostriatal afferents between the patch and matrix compartments in rats.
abstract: The striatum is divided into two compartments named the patch (or striosome) and the matrix. Although these two compartments can be differentiated by their neurochemical content or afferent and efferent projections, the synaptology of inputs to these striatal regions remains poorly characterized. By using the vesicular glutamate transporters vGluT1 and vGluT2, as markers of corticostriatal and thalamostriatal projections, respectively, we demonstrate a differential pattern of synaptic connections of these two pathways between the patch and the matrix compartments. We also demonstrate that the majority of vGluT2-immunolabeled axon terminals form axospinous synapses, suggesting that thalamic afferents, like corticostriatal inputs, terminate preferentially onto spines in the striatum. Within both compartments, more than 90% of vGluT1-containing terminals formed axospinous synapses, whereas 87% of vGluT2-positive terminals within the patch innervated dendritic spines, but only 55% did so in the matrix. To characterize further the source of thalamic inputs that could account for the increase in axodendritic synapses in the matrix, we undertook an electron microscopic analysis of the synaptology of thalamostriatal afferents to the matrix compartments from specific intralaminar, midline, relay, and associative thalamic nuclei in rats. Approximately 95% of PHA-L-labeled terminals from the central lateral, midline, mediodorsal, lateral dorsal, anteroventral, and ventral anterior/ventral lateral nuclei formed axospinous synapses, a pattern reminiscent of corticostriatal afferents but strikingly different from thalamostriatal projections arising from the parafascicular nucleus (PF), which terminated onto dendritic shafts. These findings provide the first evidence for a differential pattern of synaptic organization of thalamostriatal glutamatergic inputs to the patch and matrix compartments. Furthermore, they demonstrate that the PF is the sole source of significant axodendritic thalamic inputs to striatal projection neurons. These observations pave the way for understanding differential regulatory mechanisms of striatal outflow from the patch and matrix compartments by thalamostriatal afferents.
authors.affiliation: Yerkes National Primate Research Center, Emory University, Atlanta, Georgia 30322, USA.
authors.forename: Dinesh V
authors.initials: DV
authors.lastname: Raju
authors.forename: Deep J
authors.initials: DJ
authors.lastname: Shah
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Wright
authors.forename: Randy A
authors.initials: RA
authors.lastname: Hall
authors.forename: Yoland
authors.initials: Y
authors.lastname: Smith
mesh_terms: D000344:Afferent Pathways / Q000166:cytology / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western / Q000379:methods; D003342:Corpus Striatum / Q000033:anatomy & histology / Q000378:metabolism*; D007839:Functional Laterality; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D016253:Microscopy, Immunoelectron / Q000379:methods; D008953:Models, Anatomic; D010835:Phytohemagglutinins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000145:classification / Q000378:metabolism* / Q000648:ultrastructure; D013788:Thalamus / Q000033:anatomy & histology / Q000378:metabolism*; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism*
chemical_list: D010835:Phytohemagglutinins; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; C100156:leukoagglutinins, plants