MECHANISMS OF ALLERGIC ITCH

1)NC小鼠自发的瘙痒-抓挠反应：在SPF条件下，NC小鼠没有表现出明显的抓挠反应，但在转移到常规环境后，抓挠反应逐渐明显增加。自发抓挠的频率与皮炎的程度大致平行，但与Ig E的血浆浓度无关。组胺和P物质不能在NC小鼠中引起抓挠。虽然5-羟色胺引起抓挠，但5-羟色胺拮抗剂不能抑制NC小鼠的自发抓挠。皮炎患者皮肤中NO浓度升高。一氧化氮合酶抑制剂可抑制皮炎小鼠皮肤神经的自发抓挠和放电，降低皮肤中一氧化氮的浓度。由于皮内注射NO供体不会引起瘙痒，所以NO可能是瘙痒增强剂而不是瘙痒原。阿片拮抗剂抑制NC小鼠皮肤神经的自发抓挠，但不抑制自发放电，提示中枢抑制…更多的行动。阿片类拮抗剂可能是治疗过敏性和特应性皮炎的有效止痒剂。2)蚊虫叮咬后的过敏性瘙痒：在幼龄小鼠中，蚊虫叮咬和注射蚊子唾液腺提取物并不明显地引起抓挠，但它们的重复逐渐增加抓挠。在反复注射唾液腺提取物的小鼠中，蚊子叮咬会引起抓挠和明显的血浆外渗。组胺H_1受体拮抗剂特非那定(30 mg/kg)几乎完全抑制这种血浆外渗，对抓挠无影响。因此，蚊子叮咬可能会引起即刻过敏的瘙痒，这种瘙痒可能不是组胺介导的。3)天然药物的止痒作用：我们检测了22种Kampo药物的止痒作用，发现Byakko-ka-nuncin-to和Kami-shouyoh-San抑制了NC小鼠的自发抓挠。由于百加忍者可降低皮肤表面温度，因此它可能至少部分参与了抗通便作用。较少

1) Spontaneous itch-scratch response of NC mice : Although NC mice did not show apparent scratching under SPF conditions, they gradually and markedly increased after transfer to conventional environment. The frequency of spontaneous scratching was roughly parallel to the degree of dermatitis, but not to the plasma concentration of IgE.Histamine and substance P did not elicit scratching in NC mice. Although serotonin elicited scratching, serotonin antagonists did not inhibit spontaneous scratching of NC mice. The concentration of NO was increased in the skin with dermatitis. NO synthase inhibitors inhibited spontaneous scratching and firing of cutaneous nerve and decreased cutaneous concentration of NO in NC mice with dermatitis. Since an intradermal injection of NO donor does not elicit scratching, NO may be itch enhancer rather than pruritogen. Opioid antagonist inhibited spontaneous scratching but not spontaneous firing of cutaneous nerve in NC mice, suggesting the central inhibitory … More action. Opioid antagonist may be effective antipruritic agent for allergic and atopic dermatitis.2) Allergic itch after mosquito bites : Although in naive mice, mosquito bites and an injection of extract of mosquito salivary gland did not apparently elicit scratching, their repetition gradually increased scratching. In mice which had been given repeated injection of the salivary gland extract, mosquito bites elicited scratching and marked plasma extravasation. The H_1 histamine receptor antagonist terfenadine (30 mg/kg) almost completely inhibited such plasma extravasation, without effect on the scratching. Thus, mosquito bites may induced itching of immediate allergy and this itching may not mediated by histamine.3) Antipruritic effects of natural medicines : We examined antipruritic effects of 22 kampo medicines and found that Byakko-ka-ninjin-to and Kami-shoyoh-san inhibited spontaneous scratching of NC mice. Since Byakko-ka-ninjin-to decreased the surface temperature of the skin, it may be at least partly involved in the antipurititic action. Less