This study found that bilateral electrolytic lesions of the ventrolateral orbital cortex(VLO)markedly reduced the inhibitory effects of high intensity electroacupuncture (EA) at "Zusanli"point on tail flick reflex in lightly anesthetized rats

but did not influence the inhibitory effects of low intensity EA stimulation. The results show that the VLO is involved in acupuncture analgesia produced by activation of snlall afferent fibers with high intensity electroacupunture. Results of this study provide further support for a hypothesis that spinal cord-Sm-VLO-PAG-spinal cord may constitute a negative feedback loop of nociceptive rnodulation. The analgesic effects produced by high intensity electroacupuncture may be mediated by this loop leading to depression of the nociceptive inputs at the spinal cord level.