Cellular localization of three vesicular glutamate transporter mRNAs and proteins in rat spinal cord and dorsal root ganglia.
Glutamate is transported into synaptic vesicles by vesicular glutamate transporter (VGLUT) proteins. Three different VGLUTs, VGLUT1, VGLUT2, and VGLUT3, have recently been characterized, and they are considered to represent the most specific marker so far for neurons using glutamate as transmitter. We analyzed the cellular localization of VGLUT1-3 in the rat spinal cord and dorsal root ganglia (DRGs) in control rats and after dorsal rhizotomy. Using in situ hybridization, VGLUT1 mRNA containing neurons were shown in the dorsomedial part of the intermediate zone, whereas VGLUT2 mRNA-expressing neurons were present in the entire intermediate zone, both populations most likely representing interneurons. VGLUT3 mRNA could not be detected in the spinal cord. In the ventral horn, a dense plexus of VGLUT1-immunoreactive (ir) nerve terminals was present, with large varicosities abutting on presumed motoneurons. In the dorsal horn a similarly dense plexus was seen, except in laminae I and II. A very dense plexus of VGLUT2-ir fibers was distributed in the entire gray matter of the spinal cord, with many fibers lying close to presumed motoneurons. Few VGLUT3-ir fibers were distributed in the white and gray matter, including lamina IX. However, a dense VGLUT3-ir plexus was seen in the sympathetic intermedio-lateral column (IML). Multiple-labeling immunohistochemistry revealed that the VGLUT1-, VGLUT2-, and VAChT-containing varicosities in lamina IX all represent separate entities. There was no colocalization of VGLUT3 with VAChT or 5-HT in varicose fibers of the ventral horn, but some VGLUT3-ir fibers in the IML were 5-HT-positive. Lesioning of the dorsal roots resulted in an almost complete disappearance of VGLUT1-ir fibers around motoneurons and a less pronounced decrease in the remaining gray matter, whereas the density of VGLUT2- and VAChT-ir fibers appeared unaltered after lesion. Many VGLUT1-ir neurons were observed in DRGs; they were almost all large and did not colocalize calcitonin gene-related peptide (CGRP), and there was no overlap between these markers in fibers in the superficial dorsal horn. VGLUT2 was, at most, seen in a few DRG neurons. Taken together, these results suggest that the VGLUTs mRNAs are present in distinct subsets of neuronal populations at the spinal level. VGLUT1 is mainly present in primary afferents from large, CGRP-negative DRG neurons, VGLUT2 has mainly a local origin, and VGLUT3 fibers probably have a supraspinal origin.
Oliveira
Alexandre L R
AL
Department of Neuroscience, The Retzius Laboratory, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
Hydling
Fredrik
F
Olsson
Eric
E
Shi
Tiejun
T
Edwards
Robert H
RH
Fujiyama
Fumino
F
Kaneko
Takeshi
T
Hökfelt
Tomas
T
Cullheim
Staffan
S
Meister
Björn
B
D026922:Amino Acid Transport Systems, Acidic / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004525:Efferent Pathways / Q000166:cytology / Q000378:metabolism; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D007395:Interneurons / Q000166:cytology / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology*; D050494:Vesicular Acetylcholine Transport Proteins; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D050496:Vesicular Glutamate Transport Proteins; D033921:Vesicular Transport Proteins
D026922:Amino Acid Transport Systems, Acidic; D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D012333:RNA, Messenger; C460879:SLC17A8 protein, human; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; C493461:Slc18a3 protein, rat; D050494:Vesicular Acetylcholine Transport Proteins; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D050496:Vesicular Glutamate Transport Proteins; D033921:Vesicular Transport Proteins; D012701:Serotonin; D018698:Glutamic Acid