A study team headed by Dr. ZHANG Xu, Institute of Neuroscience, a part of the Chinese Academy of Sciences, has found that the Delata-opioid system is involved in modulation of pain transmission in the spinal cord. |?-opioid receptors (DORs) are induced by stimulus-triggered exocytosis of DOR-containing large dense-core vesicles (LDCVs). This interaction is mediated by the substance P domain of protachykinin and the third luminal domain of DOR.  Furthermore, deletion of the preprotachykinin A gene reduced stimulus-induced surface insertion of DORs and abolished DOR-mediated spinal analgesia and morphine tolerance. Thus, protachykinin is essential for modulation of the sensitivity of nociceptive afferents to opioids, and the opioid and tachykinin systems are directly linked by protachykinin/DOR interaction. The finding was published in the August 25^th issue of Cell.