The present study was performed to study the effect of
2,3,7,8-tetrachlorodibenzo-p-dioxin (
TCDD) on scratching behavior in hairless mice, which are highly sensitive to pruritogens (mediators causing
itching), except for
histamine, and are suitable for time-course studies due to their hairless skin.
TCDD is a well-known
environmental pollutant that causes
skin diseases with
itching; therefore, we examined whether
TCDD induced
itching.
Oral administration of
TCDD caused no increase in scratching behavior when used alone, whereas
TCDD in combination with distilled water or
acetone/
olive oil application caused a significant increase in scratching behavior. Furthermore,
nerve growth factor (
NGF) content in the skin increased significantly. A single administration of
chlorpheniramine (
histamine H1 receptor antagonist),
tranilast (chemical mediator release inhibitor) and
olopatadine (
histamine H1 receptor antagonist) had no effect on scratching behavior induced by
TCDD in combination with
acetone/
olive oil application. With repeated administration for 7 days,
chlorpheniramine and
tranilast had no effect on scratching behavior, whereas
olopatadine significantly inhibited scratching behavior. In addition, only
olopatadine significantly inhibited
NGF content in the skin. From these findings, it can be concluded that
TCDD is not a pruritogen but causes alloknesis (itchy skin) with the simultaneous use of trivial external stimulation. In addition, it was found that drugs which decreased skin
NGF contents may inhibit this scratching behavior.