Neonatal capsaicin treatment abolishes formalin-induced spinal PGE2 release.
We investigated the effect of neonatal capsaicin treatment on formalin-evoked pain behavior and spinal levels of nociceptive neuromodulators using in vivo intrathecal microdialysis in conscious adult rats and age-matched controls. Capsaicin-treated rats displayed thermal hypoalgesia and a significant decrease in tissue content of calcitonin gene-related peptide. Paw swelling, flinching and release of spinal prostaglandin E2 induced by injection of formalin into the hindpaw were also reduced in capsaicin-treated rats compared with controls, whereas glutamate, aspartate and taurine release was unaffected. These data suggest that formalin-induced inflammation, pain behavior and spinal prostaglandin E2 release are mediated by mechanisms sensitive to neonatal capsaicin while the formalin-evoked release of amino acids in the spinal cord is not.
Hua
X Y
XY
Department of Anesthesiology, University of California, San Diego, La Jolla 92093, USA.
Calcutt
N A
NA
Malmberg
A B
AB
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D002211:Capsaicin / Q000494:pharmacology*; D015232:Dinoprostone / Q000378:metabolism*; D005557:Formaldehyde / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects*
D000596:Amino Acids; D005557:Formaldehyde; D015232:Dinoprostone; D002211:Capsaicin