Kyotorphin is a neuroactive dipeptide (Tyr-Arg) shown to have analgesic, neuroprotective, and neuromodulatory properties. It is synthesized in nerve terminals and found in the brain and in cerebro-spinal fluid (CSF). Kyotorphin indirectly stimulates opioid receptors by releasing methionine enkephalin (met-enkephalin). CSF levels are lower in patients with persistent pain and in patients with Alzheimer’;s disease.