Abstract： BACKGROUND: Experimental autoimmune myasthenia gravis(EAMG) and anti-AchR antibody of human myasthenia gravis are the same immune globulin.This antibody restricts the activity of nicotinic acetylcholine receptor and the amount of receptor binding sites is decreased,so myasthenia gravis occurs.OBJECTIVE: To observe the therapeutic effect and mechanism of action of Qiangjijianli capsule on EAMG rats.DESIGN:A randomized controlled animal experiment.SETTING: Experimental Animal Center of Guangzhou University of Traditional Chinese Medicine.MATERIALS: Acetylcholine receptors(AchR)were extracted from electric skate's electric organ which lives in the sea near Guangzhou.It had high biological activity and the protein content was 1.63 g/L.Qiangjijianli capsule (Astragalus mongholicus,Codonopsis pilosula,Atractylodes macrocephala,Angelica sinensis,Bupleurum chinense,Cairo morningglory root or leaf,Glycyrrhixa uralensis,etc.0.5 g crude drug per capsule) was bought from the Manufacturing Laboratory of Guangzhou University of Traditional Chinese Medicine with the Batch No.89-11-1.METHODS:This experiment was carried out in the Experimental Animal Center of Guangzhou University of Traditional Chinese Medicine from May to August 1990.①Adult female SD rats were immunized with AchR.The animals' movement condition was observed and recorded everyday. Ten rats were chosen as normal control group.and they were not given any treatment and raised normally.After modeled,20 successful rats were randomly assigned into 2 groups:treatmental group and model group. 2 mL Qiangjijianli capsule suspension(1 g)was intragastrically administrated into each rat of treatmental group for 30 days; The same amount of clean water was intragastrically administrated into the rats of model group for 30 days.(2)Serum AchR antibody was measured with ABC-ELISA method. After administration,the rats were sacrificed.The complete diaphragmatic muscle was extracted for in vitro receptor binding test.The constitution of N-AchR permilligram of tissue was measured with FT-603 well-type γscintillation detector and FH408 calibrater.⑧t test was used for the comparison of difference of mean value of two samples.MAIN OUTCOME MEASURES:The effect of Qiangjijianli capsule on the amount of binding site of serum AchR antibody and nicotine-like acetylcholinergic receptor(N-AChR).RESU LTS:Before Qiangjijianli capsule treatment,serum AchR antibody titre was close between model group and treatmental group(0.82±0.15 vs,0.79±0.12,P＞0.05):After Qiangjijianli capsule treatment,serum AchR antibody titre of treatmental group was significantly decreased(0,45±0.11,t=6.602,P＜0.01),and that in the treatmental group did not change significantly(0.71±0.13,P＞0.05). So,serum AchR antibody titre of treatmental group was significantly lower than that of model group(t=5.780,P＜0.01).③The number of N-AchR of normal control group was significantly more than that of model group[(1503±156)mg·min-1 vs.(1118±128)mg·min-1,t=6.034,P＜0.01].The number of N-AchR of treatmental group was significantly more than that of model group[(1277±143)mg·min-1 vs.(1118±128)mg·min-1,t=2.619,P＜0.05].③After the treatment of Qiangjijianli capsule,all of the six rats which had clinical symptoms in treatmental group did well more or less,while in model group,the six rats had no change except one.CONCLUSION: Qiangjijianli capsule can improve the symptoms of myasthenia gravis by immunological regulation and pharmacological effect of N-AchR.