[Involvement of nitric oxide in itch-scratch response of NC mice]

NC mice, a model for atopic dermatitis, showed scratching behavior when kept under conventional environment. The scratching behavior of NC mice was suppressed by distraction or by the administration of naltrexone (1 mg/kg, s.c.), an opioid antagonist. These results suggest that such scratching behavior is itch-associated response. The itch-associated response of the NC mice was significantly suppressed by an intravenous injection of nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg), but not D-NAME (10 mg/kg) and saline. Intracutaneous NO production in the rostral back, a region which the NC mice mainly scratched, was markedly increased as compared with the caudal back, a non-scratched region. The increased NO production in the rostral back of NC mice was decreased by the intravenous injection of L-NAME (10 mg/kg). These results suggest that NO and NO synthase are new target in the treatment of atopic pruritus.