Fig. 1. Effect of prostaglandin D₂ on spontaneous scratching behavior of skin-lesioned NC/Nga mice. (A) Typical intra-day inhibition pattern of topically applied prostaglandin D₂ on spontaneous scratching behavior of NC/Nga mice. The number of scratching by NC/Nga mice was measured for the first 24 h (○: Pre), followed by the next 24 h after 0.01% prostaglandin D₂ application (●: Post). ↓: Application of drug. Data represent intra-day scratching counts at each clock hour. (B) Total scratchings for 24 h of pre- or post-treatment of 0.01% prostaglandin D₂. **P<0.01 when compared with Pre value (paired Student's t-test).

Fig. 2. Effects of several prostaglandins on spontaneous scratchings by skin-lesioned NC/Nga mice. (A) The number of scratchings by NC/Nga mice was measured for the first 24 h (Pre value) followed by the next 24 h after application of each prostanoid. Inhibition (%), (Pre−Post value)×100/Pre values shown as the marker of efficacy. *P<0.05 when compared each Pre value vs. each Post value (paired Student's t-test). (B) Dose-related inhibitory activities of topically applied prostaglandins on spontaneous scratchings by NC/Nga mice. Data evaluation was done as described above. Each column or symbol and bar represents the mean±S.E.M.

Fig. 3. Effect of indomethacin on spontaneous scratchings by NC/Nga mice. (A) Typical intra-day inhibition pattern of topically applied indomethacin on spontaneous scratchings by NC/Nga mice The number of scratchings by NC/Nga mice was measured for the first 24 h (○: Pre), followed by the next 24 h after 0.1% indomethacin application (●: Post). ↓: Application of drug. Data represents intra-day scratchings at each clock hour. (B) Total scratching counts for 8 h of pre- or post-treatment of 0.1% indomethacin. *P<0.05 when compared with Pre value (paired Student's t-test).

Fig. 4. Effect of arachidonic acid on spontaneous scratchings by NC/Nga mice. (A) Typical intra-day inhibition pattern of topically applied arachidonic acid on spontaneous scratching behavior of NC/Nga mice. The number of scratchings by NC/Nga mice was measured for the first 24 h (○: Pre), followed by the next 24 h after 0.1% arachidonic acid application (●: Post). ↓: Application of drug. Data represents intra-day scratchings at each clock hour. (B) Total scratchings for 24 h of pre- or post-treatment of 0.1% arachidonic acid. *P<0.05 when compared with Pre value (paired Student's t-test).

Fig. 5. Effects of prostaglandin D₂ or indomethacin on histamine-induced scratching of ICR mice. The number of scratching behaviors of ICR mice was measured for 30 min just after intra-dermal injection of saline or histamine. 0.01% prostaglandin D₂ or 0.1% indomethacin was topically applied 1 h before histamine injection. Data represents total scratching counts for 30 min of each group. Each bar and bar represents mean±S.E.M. **P<0.01 when compared with the saline-treated group.

Anti-pruritic effects of prostaglandin D₂-related compounds in NC/Nga mice

Each value represents the means±S.E.M. (n=8). Scratching behavior was measured for 24 h (Pre value), then for 24 h after application of each compound (Post value). Inhibition % represents (Pre value−Post value)×100 Pre value. ^aP<0.05 and ^bP<0.01 were compared between each Pre value and each Post value.

Effect of indomethacin on skin prostaglandins contents in NC/Nga mice

Each value represents the means±S.E.M. pg/mg tissue weight (n=6). Indomethacin; 0.2 ml of 0.1% indomethacin was topically treated to mouse back skin, 1 h before the experiment. ^aP<0.05, ^bP<0.01 and ^cP<0.001 compared with non-treatment group of each prostaglandins.

Effect of arachidonic acid on skin prostaglandins contents in NC/Nga mice

Each value represents the means±S.E.M. pg/mg tissue weight (n=8). Arachidonic acid; 0.2 ml of 0.1% arachnidonic acid was topically treated to mouse back skin, 1 h before the experiment. ^aP<0.05 compared with non-treatment group of each prostaglandins.