Evaluation of behavior and neuropeptide markers of pain in a simple, sciatic nerve-pinch pain model in rats.
Pathomechanisms of injured-nerve pain have not been fully elucidated. Radicular pain and chronic constriction injury models have been established; however, producing these models is complicated. A sciatic nerve-pinch injury is easy to produce but the reliability of this model for evaluating pain behavior has not been examined. The current study evaluated pain-related behavior and change in pain markers in the dorsal root ganglion (DRG) of rats in a simple, sciatic nerve-pinch injury model. In the model, the sciatic nerve was pinched for 2 s using forceps (n = 20), but not injured in sham-operated animals (n = 20). Mechanical and thermal hyperalgesia were measured every second day for 2 weeks using von Frey filaments and a Hargreaves device. Calcitonin gene-related peptide (CGRP), activating transcription factor-3 (ATF-3), phosphorylated p38 mitogen activated protein (Map) kinase (p-p38), and nuclear factor-kappa B (NF-κB; p65) expression in L5 DRGs were examined at 4 and 7 days after surgery using immunohistochemistry. The proportion of neurons immunoreactive for these markers was compared between the two groups. Mechanical (during 8 days) and thermal hyperalgesia (during 6 days) were found in the pinch group rats, but not in the sham-operated animals (p < 0.05); however, hyperalgesia was not significant from days 10 to 14. CGRP, ATF-3, p-p38, and NF-κB expression in L5 DRGs was upregulated in the nerve-injured rats compared with the sham-operated rats (p < 0.01). Our results indicate that a simple sciatic nerve pinch produced pain-related behavior. Upregulation of the pain-marker expression in the nerve-injury model suggested it could be used as a model of pain. However, it was not considered as suitable for long-term studies.
Hirose
Kazutoshi
K
Department of Orthopaedic Surgery, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
Iwakura
Nahoko
N
Orita
Sumihisa
S
Yamashita
Masaomi
M
Inoue
Gen
G
Yamauchi
Kazuyo
K
Eguchi
Yawara
Y
Ochiai
Nobuyasu
N
Kishida
Shunji
S
Nakamura
Junichi
J
Takaso
Masashi
M
Ishikawa
Tetsuhiro
T
Arai
Gen
G
Miyagi
Masayuki
M
Kamoda
Hiroto
H
Aoki
Yasuchika
Y
Hiwatari
Ryo
R
Kakizaki
Jun
J
Kunishi
Toshikazu
T
Kono
Motoaki
M
Suzuki
Takane
T
Toyone
Tomoaki
T
Takahashi
Kazuhisa
K
Kuniyoshi
Kazuki
K
Ohtori
Seiji
S
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D015415:Biomarkers / Q000378:metabolism; D004195:Disease Models, Animal; D008297:Male; D009479:Neuropeptides / Q000378:metabolism*; D010146:Pain / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012585:Sciatica / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology*
D015415:Biomarkers; D009479:Neuropeptides