title: Pharmacological characterization of capsaicin-induced body movement of neonatal rat.
abstract: In neonatal rats, nociceptive responses induced by capsaicin were characterized pharmacologically. Capsaicin, injected subcutaneously (s.c.), induced body movement including scratching and struggling responses, and the responses were quantified by using a device composed of an audio speaker as a detector. The capsaicin-induced body movement was inhibited by a tachykinin NK1-receptor antagonist RP-67580 with an ID50 value of 3.5 mg/kg, s.c. Opioid analgesics, morphine, buprenorphine and pentazocine, also inhibited the body movement with ID50 values of 0.085, 0.0079 and 0.92 (mg/kg, s.c.), respectively. Non-steroidal anti-inflammatory drugs, indomethacin, ibuprofen and acetaminophen, did not exert any effect on the capsaicin-induced body movement. Neither the sedative diazepam nor the sedative chlorpromazine inhibited the body movement. It is concluded that the capsaicin-induced body movement in neonatal rats, which is considered to be nociceptive responses mediated by substance P, is sensitive to centrally acting analgesics with micro-opioid receptor agonist activity.
authors.affiliation: Biological Research Laboratories, Sankyo Co., Ltd., Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kubota
authors.forename: M
authors.initials: M
authors.lastname: Kubota-Watanabe
authors.forename: K
authors.initials: K
authors.lastname: Fujibayashi
authors.forename: K
authors.initials: K
authors.lastname: Saito
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002211:Capsaicin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D009068:Movement / Q000187:drug effects*; D018847:Opioid Peptides / Q000494:pharmacology; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D006993:Hypnotics and Sedatives; D018847:Opioid Peptides; D002211:Capsaicin