OBJECTIVETo observe the effect of needling "Housanli" (ST 36) with different retaining-needle time on the pain threshold of mice using the hot water tail-flick test, and investigate the relationship between the retaining-needle time and the therapeutic effect.

METHODSTwenty-four healthy mice were randomly divided into four groups: no retaining-needle group (group A), retaining-needle 10 min group (group B), retaining-needle 20 min group (group C) and retaining-needle 30 min group (group D), with 6 mice for each group. After acupuncture "Housanli", the tail of mouse was put into the hot water at 50 degrees C, and the intervening time from the tail entered water to the tail flicked out of water was recorded and analyzed for each group.

RESULTSAfter acupuncturing "Housanli", the pain threshold was significantly improved with the hot water tail-flick test in both group A and group C (both P<0.01), however, there was no significant difference in both group B and group D (both P>0.05). Within 30 min of retaining-needle, the effect curve of acupuncture analgesia was showed in a waved line. In contrast, the maximum value of latent period on the tail-flick was detected in the group C that was the biggest effect of acupuncture analgesia among the four groups.

CONCLUSIONThe best retaining-needle time of hand-acupuncture for acupuncture analgesia is 20 min.