Involvement of µ-opioid Receptors and κ-opioid Receptors in Itch-related Scratching Behaviour of Imiquimod-induced Psoriasis-like Dermatitis in Mice

• Main Authors: Nobuaki Takahashi, Mitsutoshi Tominaga, Ryohei Kosaka, Yayoi Kamata, Yoshie Umehara, Hironori Matsuda, Azumi Sakaguchi, Hideoki Ogawa, Kenji Takamori
• Format: Article
• Language: English
• Published: Society for Publication of Acta Dermato-Venereologica 2017-06-01
• Series: Acta Dermato-Venereologica
• Subjects: imiquimod; itch; opioidreceptor; psoriasis
• Online Access: https://www.medicaljournals.se/acta/content/html/10.2340/00015555-2704
• ISSN: 0001-5555; 1651-2057

The pathogenesis of psoriatic itch is poorly understood. The aim of this study was to investigate the involvement of opioid receptors in scratching behaviour of imiquimod-induced psoriasis-like dermatitis model mice. Topical application of 5% imiquimod cream to the rostral back skin of mice induced antihistamine-resistant scratching behaviour. The expression of µ-opioid receptor (MOR) protein increased in the epidermis, dorsal root ganglia (DRG) and spinal cord of imiquimod-treated mice. In contrast, the expression of κ-opioid receptor (KOR) protein decreased in the DRG and spinal cord of imiquimod-treated mice, and was undetectable in the epidermis of both groups. Topical or intraperitoneal administration of the MOR antagonist naloxone and oral administration of the centrally acting KOR agonist ICI-199,441 inhibited scratching behaviour, whereas oral administration of the peri­pherally-selective KOR agonist asimadoline did not. These results suggest that peripheral and central MOR and central KOR may be involved in the modulation of scratching behaviour in imiquimod-treated mice.