1. The release of Naga peptide in central grey of rabbit was incread signifi- cantly after acupuncture. 2. The content of Naga peptide in CSF was increased markedly after acupuncture

and the pain threshold of the rabbit was also increased

markedly at the same time. The increment of Naga was parallel to the rise of pain thrashold. 3. The amount of Naga peptide in CSF was increased markedly after injection of Naga ino the vein and the Pain threshold of the rabbit was also increased markedly at the same time. The increment of Naga in CSF was parallel to the rise of pain threshold. 4. Naga peptide in CSF was increased markedly after acupuncture

or increased significantly after injection into the vein. The changes of Naga in CSF were parallel to the changes of pain threshold. Thes results show that Naga may be one of the endogenous opioid peptide and related to the acupuncture.