Itch-associated response induced by intradermal serotonin through 5-HT2 receptors in mice

Neurosci Res. 1999 Nov;35(2):77-83. doi: 10.1016/s0168-0102(99)00070-x.


Serotonin (5-HT) is pruritogenic in humans and suggested to be involved in some pruritic diseases. Our experiments were carried out to determine whether an intradermal injection of 5-HT would elicit itch-associated response in mice and to elucidate the 5-HT receptor subtypes involved in this 5-HT action. 5-HT (14.1-235 nmol site(-1)) injected intradermally into the rostral back elicited scratching of the injected site, with bell-shaped dose-response relationship. The scratching induced by 5-HT (100 nmol site(-1), peak effective dose) was suppressed by capsaicin (repeated administration) and the opioid antagonist naloxone, features being similar to human itching. Scratching was also elicited by the 5-HT2 receptor agonist alpha-methylserotonin, but not by the 5-HT1A receptor agonist R(+)-8-hydroxy-N,N-dipropyl-2-aminotetralin nor the 5-HT3 receptor agonists 2-methylserotonin and 1-phenylbiganide. Scratching induced by 5-HT and alpha-methylserotonin was inhibited by peroral pretreatment with 5-HT1/2 receptor antagonists methysergide and cyproheptadine. 5-HT-induced scratching was also inhibited by intradermal injection of methysergide. Peroral pretreatment with 5-HT3 receptor antagonists ondansetron and 3-tropanyl-3, 5-dichrobenzoate did not significantly suppress 5-HT-induced scratching. The results suggest that scratching induced by intradermal injection of 5-HT is itch-associated response. The 5-HT action may be mediated at least partly by cutaneous 5-HT2 receptors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Behavior, Animal / drug effects
  • Capsaicin / pharmacology
  • Dose-Response Relationship, Drug
  • Histamine / administration & dosage
  • Injections, Intradermal
  • Male
  • Mice
  • Mice, Inbred Strains
  • Naloxone / pharmacology
  • Narcotic Antagonists / pharmacology
  • Pruritus / chemically induced*
  • Reaction Time / drug effects
  • Receptors, Serotonin / metabolism*
  • Serotonin / administration & dosage*
  • Serotonin Antagonists / pharmacology
  • Serotonin Receptor Agonists / pharmacology


  • Narcotic Antagonists
  • Receptors, Serotonin
  • Serotonin Antagonists
  • Serotonin Receptor Agonists
  • Serotonin
  • Naloxone
  • Histamine
  • Capsaicin