Abstract
Scratching behavior observed after epicutaneous challenge with the antigen 2,4-dinitrofluorobenzene (DNFB) in the ear of BALB/c mice passively sensitized with anti-dinitrophenol (DNP). Immunoglobulin (Ig) E was characterized pharmacologically and compared with that caused by compound 48/80. Although DNFB application itself caused scratching behavior in non-sensitized mice, the number of scratchings apparently increased in sensitized mice from 60min after antigen application in comparison with non-sensitized control mice. Prednisolone, cyproheptadine, dibucaine and naloxone significantly inhibited the DNFB-induced scratching behavior, whereas the histamine H1-receptor antagonists HSR-609, cetirizine and terfenadine only showed a tendency to inhibit scratching. Injection of 48/80 into the rostral part of the back also caused scratching. The first scratching was observed within 10min after injection and lasted intermittently for 30min. The 48/80-induced scratching was markedly inhibited by cyproheptadine, dibucaine and naloxone, but not by prednisolone and the histamine H1-receptor antagonists. Ear edema caused by DNFB application in sensitized mice was markedly inhibited by prednisolone, HSR-609, cetirizine, terfenadine and cyproheptadine, whereas dibucaine and naloxone failed to affect ear edema. These results indicate that scratching behavior could be induced in mice in association with an IgE- mediated allergic cutaneous reaction and that the reaction is pharmacologically similar, but not identical, to that caused by 48/80. Although histamine is considered to participate in the formation of ear edema, it may not play an important role in the generation of scratching.
