Objective To explore the pathyologic basis of qi stagnation. Methods Twenty healthy male Wistar rats were randomized into normal group and model group. The rat models with Qi stagnation were established by chronic constraint for 6 weeks. The general condition including spirit

weight

food and sucrose water intake of the models were recorded. The level of serum cortisone （CORT）

plasma angiotensin Ⅱ （AngⅡ）

endothelin （ET）

serum 5-hydroxy-trytamine （5-HT）

norepinephrine （NE）

epinephrine （E）

and nitric oxide （NO） were measured. The thymus and adrenal gland indices were calculated. Changes in ultrastructure of thoracic aorta endothelial cells were observed with transmission electron microscope. Results Compared with the normal group

the model rats showed listlessness

slow response

reduction of diet

and weight increase becoming slower

food intake

sucrose water intake

and weight were significantly reduced （P<0.01）. The level of plasma ET

AngⅡ

serum CORT

NE

and E of the model group increased significantly

and the level of NO and 5-HT decreased （P<0.05 or P<0.01）. The thymus and spleen indices were significantly lowered （P<0.05）

and the ultrastructure of thoracic aortic endothelial cells was obvious changed. Conclusion The model rats with Qi stagnation have obvious endothelial damage in the structure and function. Their neural-endocrine-immune system disorder serves as the pathyological basis of qi stagnation.