Expression and co-expression of VR1, CGRP, and IB4-binding glycoprotein in dorsal root ganglion neurons in rats: differences between the disc afferents and the cutaneous afferents.
METHODS
The expression of vanilloid receptor 1 (VR1), calcitonin gene-related peptide (CGRP), and isolectin B4 (IB4)-binding glycoprotein in dorsal root ganglion (DRG) neurons innervating the lumbar disc and the plantar skin was investigated.


OBJECTIVE
To characterize the DRG neurons innervating lumbar discs and those innervating cutaneous tissue in rats.


BACKGROUND
Small nociceptive DRG neurons are divided into nerve growth factor (NGF) sensitive and glial cell line-derived neurotrophic factor (GDNF)-sensitive neurons. CGRP and IB4-binding glycoprotein are recognized as specific markers for NGF and GDNF-sensitive neurons, respectively. VR1 is localized in small DRG neurons.


METHODS
Using histochemical staining and retrograde tracing methods, the expression of VR1, CGRP, and IB4-binding glycoprotein in DRG neurons innervating the L5-L6 disc and the plantar skin was examined in rats.


RESULTS
DRG neurons innervating the disc showed positive staining as: 23.4% VR1, 54.4% CGRP, and 1.0% IB4-binding glycoprotein. The following distribution was found for DRG neurons innervating the skin: 35.1% VR1, 41.1% CGRP, and 19.5% IB4-binding glycoprotein. Percentages of neurons positive for VR1 and IB4-binding glycoprotein were significantly lower in DRG neurons innervating the disc than in DRG neurons innervating the skin (P < 0.05), while no significant difference was observed in the percentage of neurons positive for CGRP.


CONCLUSIONS
VR1 is less abundant in lumbar disc than in cutaneous tissue. Our data suggest that nociceptive information from the disc is transmitted mostly by NGF-sensitive neurons, while that from the cutaneous tissue is transmitted by both NGF-sensitive and GDNF-sensitive neurons.
Aoki
Yasuchika
Y
Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan. yasuaoki@h6.dion.ne.jp
Ohtori
Seiji
S
Takahashi
Kazuhisa
K
Ino
Hidetoshi
H
Douya
Hideo
H
Ozawa
Tomoyuki
T
Saito
Tomoko
T
Moriya
Hideshige
H
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D048429:Cell Size; D005727:Ganglia, Spinal / Q000166:cytology*; D006023:Glycoproteins / Q000378:metabolism*; D007150:Immunohistochemistry; D007403:Intervertebral Disc / Q000294:innervation; D037102:Lectins / Q000378:metabolism*; D008297:Male; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism*; D009619:Nociceptors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000294:innervation; D050916:TRPV Cation Channels / Q000378:metabolism*; D053675:Versicans
D015415:Biomarkers; D006023:Glycoproteins; D037102:Lectins; D050916:TRPV Cation Channels; C494484:TRPV1 receptor; C508324:Vcan protein, rat; D053675:Versicans; D015740:Calcitonin Gene-Related Peptide