Intracisternal, but not intrathecal, injection of naloxone inhibits cutaneous itch-related response in mice.
The present study was conducted to determine whether cutaneous itch involves mu-opioid receptors in either of the spinal cord or lower brainstem or in both regions in mice. An intraplantar injection of serotonin hydrochloride (100 nmol/site) induced biting, an itch-related behavior. The behavior was inhibited by subcutaneous (0.3-1 mg/kg) and intracisternal (1--10 nmol/site), but not intrathecal (1--10 nmol/site), injections of naloxone hydrochloride. An intradermal injection of serotonin (100 nmol/site) to the rostral back induced scratching, an itch-related behavior, which was inhibited by subcutaneous (1 mg/kg) and intracisternal (10 nmol/site) injections of naloxone. These results suggest that mu-opioid receptor in the lower brainstem, but not spinal cord, is a site of central pruritogenic action of opioids and is involved in the facilitatory regulation of itch signaling.
Kuraishi
Yasushi
Y
Department of Applied Pharmacology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan. kuraisiy@pha.u-toyama.ac.jp
Yageta
Yuichi
Y
Konno
Mitsuhiro
M
Andoh
Tsugunobu
T
Yamaguchi-Miyamoto
Tomomi
T
Nojima
Hiroshi
H
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001933:Brain Stem / Q000187:drug effects / Q000378:metabolism; D002946:Cisterna Magna / Q000187:drug effects / Q000378:metabolism*; D007278:Injections, Spinal; D007279:Injections, Subcutaneous; D008024:Ligands; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D009292:Narcotic Antagonists / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D011537:Pruritus / Q000188:drug therapy* / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism
D008024:Ligands; D009292:Narcotic Antagonists; C404943:Oprm protein, mouse; D017450:Receptors, Opioid, mu; D012701:Serotonin; D009270:Naloxone