Neoendorphins are a group of endogenous opioid peptides derived from the proteolytic cleavage of prodynorphin. They include ñ-neoendorphin and ò-neoendorphin. The ñ-neoendorphin is present in greater amounts in the brain than ò-neoendorphin. Both are products of the dynorphin gene, which also expresses dynorphin A, dynorphin A<sub>1-8</sub>, and dynorphin B. These opioid neurotransmitters are especially active in CNS receptors, whose primary function is pain sensation. These peptides all have the consensus amino acid sequence of Tyr-Gly-Gly-Phe-Met (met-enkephalin) or Tyr-Gly-Gly-Phe-Leu (leu-enkephalin). Binding of neoendorphins to opioid receptors, in the dorsal root ganglion (DRG) neurons results in the reduction of time of calcium-dependent action potential. The ñ-neoendorphins binds to ü-opioid, ô-opioid, ú-opioid receptor (KOR), cand ò-neoendorphin binds to KOR.