Pruritus is one of the most important symptoms of allergic inflammatory skin disease. Conjugated linoleic acid (CLA) has been reported to have preventive effects against allergic inflammation. The objective of this study was to determine whether or not oral administration of CLA suppresses pruritus induced by compound 48/80 (composed of N-methyl-p-methoxy phenethylamine with formaldehyde) in mice, and if so, whether or not this effect is associated with serum histamine and prostaglandin (PG) E2 levels. Liquid CLA mixture (36.25% 9c-11t CLA, 36.95% 10t-12c CLA, 1.12% 9c-11c, and 1.94% t9-t11 CLA) was emulsified in 0.5% carboxymethyl cellulose (CMC) sodium salt and orally administered to mice at doses of 200 mg/kg once per day for 3 days. Similarly, disodium chromoglycate (DSCG), an antipruritic substance, was administered orally at the same concentrations as the negative control. Compound 48/80, a pruritus-inducing reagent, was subcutaneously injected 30 minutes after final administration of CLA. Scratching behavior of mice was counted just after compound 48/80 injection. Serum histamine and PGE2 concentrations were evaluated individually. Mice administered with CLA showed reduced frequency of scratching behavior compared to those without CLA. Antipruritic activities in CLA-treated and DSCG-treated groups were 48.5% and 26.8%, respectively. CLA and DSCG also diminished serum concentrations of histamine and PGE2 compared to compound 48/80 alone, respectively. This result suggests that dietary CLA has an antipruritic effect by down-regulating serum histamine and PGE2 levels for relief of compound 48/80-induced scratching behavior in mice, which will be useful in allergic pruritus as a preventive medicine.

Introduction
 Materials and Methods
  Chemicals and reagents
  Experimental animals
  Administaration of CLA and chemicals
  Antipruritic activity
  Blood collection
  Measurement of histamine
  Measurement of PGE2
  Statistical analysis
 Results
  CLA suppresses compound 48/80-induced pruritus
  CLA reduces the increase in level of serum histamine by compound 48/80 injection
  CLA reduces serum PGE2 level
 Discussion
 Acknowledgements
 References

• Jae-Wan Kim(Laboratory of Veterinary Internal Medicine College of Veterinary Medicine, Chungbuk National University)
• Byeong-Teck Kang(Laboratory of Veterinary Dermatology, Department of Veterinary Medicine, College of Veterinary Medicine, Chungbuk National University)
• Ji-Houn Kang(Laboratory of Veterinary Internal Medicine College of Veterinary Medicine, Chungbuk National University)
• Mhan-Pyo Yang(Laboratory of Veterinary Internal Medicine College of Veterinary Medicine, Chungbuk National University) Corresponding author