Dynorphin is a peptide produced by many different populations of neurons, which has some opiate-like activity. It is thus classed as an endogenous opioid peptide. Dynorphin is a kappa opioid receptor agonist, meaning that it acts mainly at kappa opioid receptors. Other opioid peptides include beta-endorphin, [met]-enkephalin, [leu]-enkephalin and endomorphin. Dynorphin is a product of the gene 'prodynorphin'.
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. For example, dynorphin is made in magnocellular vasopressin neurons of the supraoptic nucleus, where it is important in the patterning of electrical activity. Dynorphin produced in magnocellular oxytocin neurons is a negative feedback inhibitor of oxytocin secretion. Dynorphin produced in the arcuate nucleus and in orexin neurons of the lateral hypothalamus affects the control of appetite.