MECHANISMS OF ALLERGIC ITCH

1) NC小鼠自发挠痒反应：SPF条件下NC小鼠无明显挠痒反应，转入常规环境后逐渐显著增加。自发抓伤的频率与皮炎的程度大致平行，但与血浆IgE浓度无关。组胺和P物质不引起NC小鼠抓伤。虽然5 -羟色胺引起抓伤，但5 -羟色胺拮抗剂不抑制NC小鼠的自发抓伤。皮炎患者皮肤一氧化氮浓度升高。NO合成酶抑制剂抑制NC皮炎小鼠皮肤神经自发抓伤和放电，降低皮肤NO浓度。由于皮内注射一氧化氮供体不会引起抓挠，一氧化氮可能是瘙痒增强剂而不是瘙痒剂。阿片拮抗剂抑制NC小鼠皮神经自发抓痒，但不抑制皮神经自发放电，提示中枢抑制作用。阿片拮抗剂可能是治疗过敏性和特应性皮炎的有效止痒剂。2)蚊子叮咬后的过敏性瘙痒：虽然在幼稚小鼠中，蚊子叮咬和注射蚊子唾液腺提取物并没有明显引起抓痕，但它们的重复会逐渐增加抓痕。对反复注射唾液腺提取物的小鼠，蚊虫叮咬引起抓痕和明显的血浆外渗。H_1组胺受体拮抗剂特非那定（30 mg/kg）几乎完全抑制这种血浆外渗，对抓伤无影响。因此，蚊虫叮咬可能引起即刻过敏的瘙痒，这种瘙痒可能不是由组胺介导的。3)天然药物的止痒作用：我们检测了22种汉方药物的止痒作用，发现Byakko-ka-ninjin-to和Kami-shoyoh-san对NC小鼠自发抓痕有抑制作用。由于Byakko-ka-ninjin-to降低了皮肤的表面温度，它可能至少部分地参与了除污作用。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