title: Absence of mechanical hyperalgesia after exercise (delayed onset muscle soreness) in neonatally capsaicin-treated rats.
abstract: Delayed onset muscle soreness (DOMS) appears with some delay after unaccustomed, strenuous exercise, especially after lengthening contraction (LC). It is characterized by tenderness and movement related pain, namely muscular mechanical hyperalgesia. To clarify the involvement of C-fibers in this mechanical hyperalgesia, we examined whether DOMS could be induced in rats treated neonatally with capsaicin. We confirmed that a large portion of unmyelinated afferent fibers were lost in capsaicin treated rats. In these animals, LC failed to induce muscular mechanical hyperalgesia. mRNA of nerve growth factor (NGF) in the muscle, which plays a pivotal role in maintaining mechanical hyperalgesia, was upregulated in the capsaicin treated animals similar to the vehicle treated animals. These results demonstrate that C-fiber afferents are essential in transmitting the nociceptive information from exercised muscle in DOMS.
authors.affiliation: Department of Neuroscience II, Research Institute of Environmental Medicine, Nagoya University, Nagoya, Japan.
authors.forename: Asako
authors.initials: A
authors.lastname: Kubo
authors.forename: Michiyo
authors.initials: M
authors.lastname: Koyama
authors.forename: Ryoko
authors.initials: R
authors.lastname: Tamura
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Takagishi
authors.forename: Shiori
authors.initials: S
authors.lastname: Murase
authors.forename: Kazue
authors.initials: K
authors.lastname: Mizumura
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002211:Capsaicin / Q000633:toxicity*; D006930:Hyperalgesia / Q000139:chemically induced / Q000503:physiopathology* / Q000517:prevention & control*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology; D010146:Pain / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D010805:Physical Conditioning, Animal / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D002211:Capsaicin