title: Confocal laser scanning microscopy and ultrastructural study of VGLUT2 thalamic input to striatal projection neurons in rats.
abstract: We examined thalamic input to striatum in rats using immunolabeling for the vesicular glutamate transporter (VGLUT2). Double immunofluorescence viewed with confocal laser scanning microscopy (CLSM) revealed that VGLUT2+ terminals are distinct from VGLUT1+ terminals. CLSM of Phaseolus vulgaris-leucoagglutinin (PHAL)-labeled cortical or thalamic terminals revealed that VGLUT2 is rare in corticostriatal terminals but nearly always present in thalamostriatal terminals. Electron microscopy revealed that VGLUT2+ terminals made up 39.4% of excitatory terminals in striatum (with VGLUT1+ corticostriatal terminals constituting the rest), and 66.8% of VGLUT2+ terminals synapsed on spines and the remainder on dendrites. VGLUT2+ axospinous terminals had a mean diameter of 0.624 μm, while VGLUT2+ axodendritic terminals a mean diameter of 0.698 μm. In tissue in which we simultaneously immunolabeled thalamostriatal terminals for VGLUT2 and striatal neurons for D1 (with about half of spines immunolabeled for D1), 54.6% of VGLUT2+ terminals targeted D1+ spines (i.e., direct pathway striatal neurons), and 37.3% of D1+ spines received VGLUT2+ synaptic contacts. By contrast, 45.4% of VGLUT2+ terminals targeted D1-negative spines (i.e., indirect pathway striatal neurons), and only 25.8% of D1-negative spines received VGLUT2+ synaptic contacts. Similarly, among VGLUT2+ axodendritic synaptic terminals, 59.1% contacted D1+ dendrites, and 40.9% contacted D1-negative dendrites. VGLUT2+ terminals on D1+ spines and dendrites tended to be slightly smaller than those on D1-negative spines and dendrites. Thus, thalamostriatal terminals contact both direct and indirect pathway striatal neurons, with a slight preference for direct. These results are consistent with physiological studies indicating slightly different effects of thalamic input on the two types of striatal projection neurons.
authors.affiliation: Department of Anatomy, Zhongshan Medical School of Sun Yat-Sen University, Guangzhou, 510080, PR China. leiwl@mail.sysu.edu.cn
authors.forename: Wanlong
authors.initials: W
authors.lastname: Lei
authors.forename: Yunping
authors.initials: Y
authors.lastname: Deng
authors.forename: Bingbing
authors.initials: B
authors.lastname: Liu
authors.forename: Shuhua
authors.initials: S
authors.lastname: Mu
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Guley
authors.forename: Ting
authors.initials: T
authors.lastname: Wong
authors.forename: Anton
authors.initials: A
authors.lastname: Reiner
mesh_terms: D000818:Animals; D003342:Corpus Striatum / Q000737:chemistry / Q000166:cytology / Q000648:ultrastructure*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D008297:Male; D018613:Microscopy, Confocal / Q000379:methods; D009434:Neural Pathways / Q000737:chemistry / Q000166:cytology / Q000648:ultrastructure; D009474:Neurons / Q000737:chemistry / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013788:Thalamus / Q000737:chemistry / Q000166:cytology / Q000648:ultrastructure*; D050599:Vesicular Glutamate Transport Protein 2 / Q000502:physiology / Q000648:ultrastructure*
chemical_list: C493475:Slc17a6 protein, rat; D050599:Vesicular Glutamate Transport Protein 2