The role of TRPV1 in different subtypes of dorsal root ganglion neurons in rat chronic inflammatory nociception induced by complete Freund's adjuvant.
BACKGROUND
The present study aims to investigate the role of transient receptor potential vanilloid 1 (TRPV1) in dorsal root ganglion (DRG) neurons in chronic pain including thermal hyperalgesia and mechanical allodynia. Chronic inflammatory nociception of rats was produced by intraplantar injection of complete Freund's adjuvant (CFA) and data was collected until day 28 following injection.


RESULTS
Thermal hyperalgesia was evident from day 1 to day 28 with peak at day 7, while mechanical allodynia persisted from day 1 to day 14 and was greatest at day 7. Intrathecal administration of AMG 9810 at day 7, a selective TRPV1 antagonist, significantly reduced thermal hyperalgesia and mechanical allodynia. TRPV1 expression in DRG detected by Western blotting was increased relative to baseline throughout the observation period. Double labeling of TRPV1 with neuronal marker neurofilament 200 (NF200), calcitonin gene-related peptide (CGRP) or isolectin B4 (IB4) was used to distinguish different subtypes of DRG neurons. TRPV1 expression was increased in the medium-sized myelinated A fiber (NF200 positive) neurons and in small non-peptidergic (IB4 positive) neurons from day 1 to day 14 and was increased in small peptidergic (CGRP positive) neurons from day 1 to day 28.


CONCLUSIONS
TRPV1 expression increases in all three types of DRG neurons after CFA injection and plays a role in CFA-induced chronic inflammatory pain including thermal hyperalgesia and mechanical allodynia.
Yu
Lu
L
Neuroscience Research Institute, School of Basic Medical Sciences, Peking University, Beijing, PR China. irisyl1978@126.com
Yang
Fei
F
Luo
Hao
H
Liu
Feng-Yu
FY
Han
Ji-Sheng
JS
Xing
Guo-Gang
GG
Wan
You
Y
D000178:Acrylamides / Q000494:pharmacology; D000276:Adjuvants, Immunologic / Q000008:administration & dosage / Q000633:toxicity*; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D005620:Freund's Adjuvant / Q000008:administration & dosage / Q000633:toxicity*; D005727:Ganglia, Spinal / Q000378:metabolism*; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism; D007249:Inflammation / Q000139:chemically induced* / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D010146:Pain / Q000139:chemically induced / Q000378:metabolism*; D017288:Pain Threshold; D051381:Rats; D017207:Rats, Sprague-Dawley; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*
C500530:3-(4-t-butylphenyl)-N-(2,3-dihydrobenzo(b)(1,4)dioxin-6-yl)acrylamide; D000178:Acrylamides; D000276:Adjuvants, Immunologic; D019086:Bridged Bicyclo Compounds, Heterocyclic; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; D005620:Freund's Adjuvant