This work was to study the influence of lesion of Sm Ⅱ on effects of electroacupuncture (EA) upon nucleus raphe magnus (NRM).The experiments were performed on rats. The unit discharges of NRM neurons and their responses to noxious stimulation on tail tip were recorded extracellularly with glass microelectrode.The excitatory neurons of NRM were chosen and divided into two groups

one of them(n=10)was control before lesion of bilateral Sm Ⅱ and another (n=17) after lesion

two neurons of this group were also observed before lesion. It was found that the neurons in the contral group before lesion of sm Ⅱ could be activated by EA of "Zusanli"

the increase of spontaneous diacharges in 0-10 minutes and the 20th minute

and the decrease of their nociceptive responses in 0-25 minutes were statistically significant (P<0. 05-0. 001).But in the group after lesion the neurons were not obviously activated by EA of "Zusanli". The difference of the spontaneous discharges between the two group was statistically significant in 0-10 minutes (P<0.05-0.001)

the nociceptive reponses in 0-10 minutes and at the 20th minute (P<0. 05-0.001).The results show that integrity of Sm Ⅱ is important to acupuncture analgesia

and further suggest that information from EA of "Zusanli" could arrive at Sm Ⅱ at least partially

and then activate NRM inducing analgesia