[Effect of auricular point electrostimulation on pruritus induced by dextran in the mice]

To observe the effect of auricular electrostimulation on pruritus behavior, histomorphology and expressions of histamine 1 receptor (H1R) and transient receptor potential vanilloid subfamily 1 (TRPV1) of the scratching site, serum immunoglobulin E (IgE) and histamine (HIS) contents of pruritic mice, so as to explore its underlying mechanisms in improvement of pruritus.

Twenty-four Kunming mice were randomly divided into control, model, medication and auricular electrostimulation groups, with 6 mice in each group. The mice in the control and model groups received gavage of 0.2 mL/20 g of 0.9% sodium chloride solution, once every day for 12 d. The mice in the medication group received gavage of loratadine saline solution (1.66 mg/kg). The mice in the auricular electrostimulation group received auricular stimulation of bilateral "Xin"(Heart)-"Fei" (Lung) or margin of ear for 30 min, once daily for 12 d. In addition, all the mice in every group received grabbing-binding once every day for 12 d. One hour after the last intervention, the pruritus model was established by intravenous injection of 0.025% dextran (0.05 mL/10 g) via tail vein. The scratching response of mice was recorded, and the histopathological changes of the scratching site were observed after H.E. staining. The immunofluorescence intensities of H1R and TRPV1 were detected by immunofluorescence staining, and the contents of serum IgE and HIS were measured by using ELISA.

Compared with the control group, the model group had a decrease in the scratching latency, and an increase in the number and duration of scratching, the immunofluorescence intensities of H1R and TRPV1, and the contents of serum IgE and HIS (P<0.05). In contrast to the model group, both the medication group and auricular electrostimulation group had an increase in the scratching latency, and a decrease in the number and duration of scratching, the immunofluorescence intensities of H1R and TRPV1, and the contents of serum IgE and HIS (P<0.05). There were no significant differences between the auricular electrostimulation group and medication group in all the indexes mentioned above. H.E. staining showed cell edema in the skin epidermal tissue, a large number of lymphocytes and a few eosinophils infiltration in the dermis and subcutaneous tissue, especially around the hair follicle in the model group, while the inflammatory cells in the skin tissue of the medication group and the auricular electrical stimulation group were reduced.

Auricular electrostimulation can effectively relieve pruritus induced by dextran in mice, which may be related to its function in down-regulating the H1R/TRPV1 signaling pathway in the pruritus site.