Dynorphins are a class of peptides produced by many different populations of neurons, which has some opiate like activity. It is thus classed as an endogenous opioid peptide. The dynorphins, which include dynorphin A, dynorphin B, alpha and beta neoendorphin, and big dynorphin, are all the products of a single gene, 'preprodynorphin'. Dynorphin is produced in many different parts of the brain, including the hypothalamus, the hippocampus and the spinal cord, and has many different physiological actions, depending upon its site of production. Dynorphin is involved in modulating responses to several psychoactive substances, including cocaine. As such, it may help some individuals against addiction. Blocking dynorphin may help alleviate depression.