Changes in pain behavior and histologic changes caused by application of tumor necrosis factor-alpha to the dorsal root ganglion in rats.
METHODS
Histologic changes in the dorsal root ganglion (DRG) and the nociceptive stimulation thresholds were studied in rats.


OBJECTIVE
To examine the effects of tumor necrosis factor-alpha (TNF) with special reference to pain behavior and histology of the DRG.


BACKGROUND
Recently, it was reported that local application of nucleus pulposus induces a characteristic tissue reaction at the surface of the DRG. However, to our knowledge, there have been no previous reports about the relationship between the histologic changes and pain behavior caused by cytokines.


METHODS
Recombinant TNF was applied to the L4 DRG. Mechanical and thermal nociceptive thresholds were tested. The L4 DRG was sectioned and observed by light microscopy.


RESULTS
After the application of 5 ng/microL TNF, significant differences were observed in mechanical and thermal stimulation thresholds. At the site of application of TNF, a characteristic a semilunar-shaped enlargement was observed. The average width of the part was significantly larger in the 5 ng/microL TNF application, as compared to the 0.5-ng/microL TNF application.


CONCLUSIONS
The higher concentration of TNF used induced allodynia and hyperalgesia responses. Because the region showing the histologic changes was significantly larger after application of the higher concentration of TNF, the reaction of the DRG may be related to pain.
Murata
Yasuaki
Y
Department of Orthopaedic Surgery, School of Medicine, Chiba University, Chiba, Japan. yasuakimurata@aol.com
Onda
Akira
A
Rydevik
Björn
B
Takahashi
Ichiro
I
Takahashi
Kazuhisa
K
Olmarker
Kjell
K
D000287:Administration, Topical; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005727:Ganglia, Spinal / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D006358:Hot Temperature; D006930:Hyperalgesia / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000601:surgery; D010146:Pain; D017288:Pain Threshold / Q000187:drug effects* / Q000502:physiology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins; D012684:Sensory Thresholds / Q000187:drug effects; D014110:Touch / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D021801:Zygapophyseal Joint / Q000601:surgery
D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha