Dynorphin A is an endogenous opioid peptide involved in inhibitory neurotransmission in the central nervous system (CNS). Dynorphin A is a highy potent kappa opioid receptor (KOR) agonist, and is also an agonist for other opioid receptors, such as mu (MOR) and delta (DOR). Dynorphin A can induce neuronal death, and can be used in the research of neurological disease.