Outlet obstruction constipation(OOC)is a common clinical problem affecting many people's daily life quality nowadays.Acupuncture therapy is effective in easing OOC to reduce patients' sufferings by stimulation of Baliao-points i.e.

bilateral Shangliao(BL 31)

Ciliao(BL 32)

Zhongliao(BL 33)and Xialiao(BL 34)

which has been confirmed repeatedly in clinical practice.In the present paper

the authors reviewed development of studies on the underlying mechanisms of acupuncture stimulation of Baliao-points for OOC from:1)lowering the sensitivity of intraganglionic laminar nerve endings(rIGLEs)to rectal mechanical distension during defecation

2)raising the level of circulating cholecystokinin(CCK)to improve the sensory threshold of the rectum

3)lowering the excitability ofγ-motor neurons in the spinal anterior horns controlling the slow contraction of the rectal sphincter muscle

4)inhibiting the excitability of sympathetic output from the spinal lateral horns

5)easing the tonic contraction of the pelvic muscles to reduce the release of 5-hydroxy tryptamine(5-HT)

histamine

and other related chemical mediators due to local ischemia.Moreover

further study on the mechanism of acupuncture stimulation of Baliao-points underlying improving OOC may help up find more specific and effective therapeutic targets and provide more reliable experimental foundation and theoretical basis.