| IntroductionHistamine has been recognized as a major pathogenetic mediator of allergic disorders. The exact mechanism of action remained unknown until 1966 when the histamine H, receptor was identified. The first H1 - receptor antagonists became commercially available in the 1940s and were widely prescribed subsequently. Compared with the first generation of antihistamines, the side effects of the second generation had been apparently reduced. With the application of several types of HI - receptor antagonists on murine contact dermatitis model, the curative effect of the first and second generation antihistamines on the murine contact dennatitis model had been observed, and these results can be taken as the theoretical evidence for clinical application of the antihistamines for the treatment of type - IV allergic reactions. Beside this, we had also investigate the influence of these antihistamines on the number changes of different positive antibody epidermal LCs ( Langerhans cells) and dendritic epidermal cell ( DEC ) , which play an important role in delayed hypersensitive reaction.Materials and Methods1. Animal: 615 syngeneic mice, male, 20 ±2g weight;2. Reagent and instruments: DNCB, McAb 0X3, 0X4, jij, 22.1 ,ABC reagent box, Olympus optical microscope.3. Method; 40 mice of 615 syngeneic system were randomly divided into 5 groups, i. e. mizolastine group, loratadine group, chlort-rimeton group, dexamethason group and 1% twen 80 group. Induce contact dermatitis on each group, P. O, measure the variations of the left ear thickness of the mice. Cut off sample skin and process it with immunohistochemical staining.4. Index to be observed: Measure the variations of the thickness at the middle part of left ear, compute the difference of the thickness within 24 hours before and after induction. Count the number of LCs and DEC.Results1. Measure the thickness at the middle part of the left ear of the mice continuously within one week.2. Difference between each group: mizolastine group is more effective than loratadine group and chlortrimeton group. No difference between loratadine group and chlortrimeton group.3. Effects of different antihistamines on 0X3 + LCs and OX4+ LCs: Compared to the normal control group, the OX3 + LCs of these experimental groups had been greatly reduced, and the number of positive cells of mizolastine group is apparently less than that of loratadine group and chlortrimeton group.4. Effect of antihistamines on jij and 22.1 positive Thy - 1 DEC: The number of jij positive DEC of testing groups is less than the normal control group, mizolastine group is less than loratadine group. As to the number of 22.1 positive DEC, the mizolastine group and loratadine group is less than the normal control group, but no difference hadbeen observed between chlortrimeton group and the normal control group.DiscussionIn the research of allergic contact dermatitis, the delayed hypersensitive reaction model, i. e. DNFB, have already been adopted as animal model. The author also prepared the animal model of allergic contact dermatitis. The representative aritihistamines of the first and second generation, that is chlortrimeton (1st generation) , mizolastine and loratadine (2ndgeneration) , are used as experimental groups, one of the corticosteroid, dexamethasone was used as positive control. With the animal model of murine allergic contact dermatitis induced by DNFB, the effects of H1 - receptors include mizolastine etc. have been studied, the results shows that all these antagonists more or less have suppressive effects on murine allergic contact dermatitis.The curative mechanism of H1 -receptors antagonists is that they can competitively take effect cells from histamines receptors. According to this mechanism, they are mainly used on type -1 allergic reaction, but in the clinical applications, they are also widely applied to type - IV ones, and the correspondent mechanism is still unknown.Contact dermatitis is the clinical diagnosis of an infla... |
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