The time course of inflammatory cytokine secretion in a rat model of postoperative pain does not coincide with the onset of mechanical hyperalgesia.
We characterized the time course of inflammatory cytokine release at the site of injury and in plasma after surgery on the rat tail. Anesthetized Sprague-Dawley rats had a 20 mm long incision made through the skin and fascia of their tails. Control rats were anesthetized, but no incision was made. Blood and tissue samples were taken 2 h and 1, 2, 4, and 8 days after surgery and analysed by ELISA for interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and cytokine-induced neutrophil chemoattractant-1 (CINC-1). In another group of rats, daily behavioral measurements were made of the rats' responses to a blunt noxious mechanical stimulus (4 Newtons) applied to their tails. Primary hyperalgesia developed within 2 h of surgery and lasted for 6 days. The tissue concentrations of IL-1beta, IL-6, and CINC-1 increased within 24 h of surgery, and TNF-alpha concentration increased within 48 h of surgery. Thereafter, cytokine concentrations remained elevated for 4 (IL-1beta and IL-6) to 8 days (CINC-1, TNF-alpha) after surgery. Control animals did not develop hyperalgesia and no changes in cytokines concentrations were detected. Thus, in our model of postoperative pain, secretion of inflammatory cytokines IL-1beta, IL-6, TNF-alpha, and CINC-1 was not essential for the initiation of postoperative hyperalgesia.
Loram
Lisa C
LC
Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, South Africa.
Themistocleous
Andreas C
AC
Fick
Linda G
LG
Kamerman
Peter R
PR
D000818:Animals; D054360:Chemokine CXCL1; D019743:Chemokines, CXC / Q000097:blood / Q000378:metabolism; D016207:Cytokines / Q000097:blood / Q000378:metabolism*; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006930:Hyperalgesia / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*; D007249:Inflammation / Q000097:blood / Q000139:chemically induced / Q000378:metabolism; D018836:Inflammation Mediators / Q000097:blood / Q000378:metabolism*; D053583:Interleukin-1beta / Q000097:blood / Q000378:metabolism; D015850:Interleukin-6 / Q000097:blood / Q000378:metabolism; D008297:Male; D010149:Postoperative Pain / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013623:Tail / Q000601:surgery; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000097:blood / Q000378:metabolism; D015854:Up-Regulation