Activation of ERK in the rostral ventromedial medulla is involved in hyperalgesia during peripheral inflammation.
We have previously shown that the extracellular signal-regulated kinase (ERK) is activated in the rostral ventromedial medulla (RVM) during peripheral inflammation. In the present study, the relationship between ERK signaling in the RVM and pain hypersensitivity was investigated in the rat. Microinjection of U0126, a mitogen-activated protein kinase kinase inhibitor, into the RVM decreased phosphorylated ERK at 7 h after complete Freund's adjuvant (CFA) injection into the hindpaw. The U0126 microinjection also attenuated thermal hyperalgesia in the ipsilateral hindpaw at 24 h after CFA injection. The ipsilateral paw withdrawal latency in the U0126 group (67.9%+/-5.3% vs. baseline, n=7) was significantly longer than that in the control group (52.0%+/-3.6% vs. baseline, n=8). These findings suggest that activation of ERK in the RVM contributes to thermal hyperalgesia during peripheral inflammation.
Department of Physiology, Wakayama Medical University, Kimiidera 811-1, Wakayama City, 641-8509, Japan. imbe@wakayama-med.ac.jp
Hiroki
H
Imbe
Akihisa
A
Kimura
Keiichiro
K
Okamoto
Tomohiro
T
Donishi
Fumiko
F
Aikawa
Emiko
E
Senba
Yasuhiko
Y
Tamai
D000818:Animals; D004525:Efferent Pathways / Q000187:drug effects / Q000201:enzymology / Q000503:physiopathology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005620:Freund's Adjuvant; D006614:Hindlimb / Q000503:physiopathology; D006930:Hyperalgesia / Q000139:chemically induced / Q000503:physiopathology*; D007249:Inflammation / Q000139:chemically induced / Q000503:physiopathology*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000201:enzymology / Q000503:physiopathology; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D010525:Peripheral Nerves / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012018:Reflex / Q000187:drug effects / Q000502:physiology; D012154:Reticular Formation / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D011984:Sensory Receptor Cells / Q000503:physiopathology
D004791:Enzyme Inhibitors; D005620:Freund's Adjuvant; D048049:Extracellular Signal-Regulated MAP Kinases; D048052:Mitogen-Activated Protein Kinase 3