Spinorphin (LVVYPWT) has been isolated from the bovine spinal cord as an endogenous inhibitor of enkephalin-degrading enzymes. Spinorphin has an antinociceptive effect, inhibitory effect on contraction of smooth muscle and anti-inflammatory effect. It can enhance the inhibitory effect of enkephalin on allodynia induced by nociceptin, which are due to inhibition of enkephalin-degrading enzymes. And its inhibitory effects can be antagonized by Naloxone.