Dynorphin A, also known as dynorphin A, is an endogenous opioid peptide. It is derived from the precursor protein, prodynorphin, and is released by the cleavage of proprotein convertase 2. The peptide mainly binds to κ-opioid receptors, but can also affect other types of opioid receptors. Dynorphin A participates in inhibitory neurotransmission in the central nervous system, can block currents activated by NMDA receptors, and may play a key physiological role through its metabolites.