Objective To observe the effect of balance acupuncture on the thermal pain threshold and plasma β-endorphin(β-EP) and adrenocorticotrophic hormone(ACTH) levels in lumbar disc herniation rats so as to research its mechanisms underlying improvement of lumbar disc protrusion.Methods A total of 120 male rats were randomly divided into blank control(control) group

model group

sham-operation(sham)group

and acupuncture group(n=30) which were further divided into 7-days(d) and 14-d subgroups.Rats in the acupuncture group were treated with balance acupuncture of "Back Pain" point(the midpoint between two eyes) and "Hip Pain"point(the midpoint between the acromial process and the axillary furrow).Thermal pain threshold was detected by using radiant heat detector.Plasma β-EP and ACTH levels were determined by radioimmunoassay.Results Compared with the control group and pre-operation and sham group

the thermal pain reaction was increased significantly in the model group(P<0.05).In comparison with the model group

the thermal pain reaction was decreased obviously from day 10 after acupuncture treatment in the acupuncture group(P<0.05).Compared to the control group

plasma β-EP contents on day 7 and 14 and ACTH level on day 14 in the model group were increased significantly(P<0.05)

while in comparison with the model group

plasma β-EP contents on day 7 and 14 and ACTH level on day 14 in the acupuncture group were down-regulated markedly(P<0.05).No significant difference were found between the control and sham groups in plasma β-EP contents and ACTH levels on day 7 and 14(P>0.05).Conclusion Balance acupuncture treatment can lower plasma ACTH level in lumbar disc herniation rats

which may contribute to its effect in easing lumbar disc herniation pain in clinic practice.