Neoendorphins are a group of endogenous opioid peptides derived from the proteolytic cleavage of prodynorphin.^[1] They include α-neoendorphin and β-neoendorphin. The α-neoendorphin is present in greater amounts in the brain than β-neoendorphin. Both are products of the dynorphin gene, which also expresses dynorphin A, dynorphin A-(1-8), and dynorphin B.^[2] These opioid neurotransmitters are especially active in Central Nervous System receptors, whose primary function is pain sensation.^[3] These peptides all have the consensus amino acid sequence of Try-Gly-Gly-Phe-Met (met-enkephalin) or Tyr-Gly-Gly-Phe-Leu ( leu-enkephalin).^[4] Binding of neoendorphins to opioid receptors (OPR), in the dorsal root ganglion (DRG) neurons results in the reduction of time of calcium-dependent action potential.^[5] The α-neoendorphins bind OPRD1(delta), OPRK1(kappa), and OPRM1 (mu) and β-neoendorphin bind OPRK1.^[6][7]

• Endorphin