N-terminally acetylated Leu-enkephalin

Enkephalins (met- , leu-enkephalin, and enkephalin 8) and dynorphins are two classes of opioid peptides found in the spinal dorsal horn. Mu, delta, and kappa are three major subtypes of opioid receptors. Enkephalins are putative endogenous ligands for delta opioid receptors, and dynorphins are endogenous ligands for the kappa opioid receptors. Three receptor types resembling the vertebrate δ- and κ-type opioid receptors have been characterized pharmacologically in nervous tissues (e.g. K _i =18.9 nM for Leu-enkephalin) and localized by autoradiography at CHH terminals in the SG of C. maenas .