Definition: The endogenous peptides with opiate-like activity. The three major classes currently recognized are the ENKEPHALINS, the DYNORPHINS, and the ENDORPHINS. Each of these families derives from different precursors, proenkephalin, prodynorphin, and PRO-OPIOMELANOCORTIN, respectively. There are also at least three classes of OPIOID RECEPTORS, but the peptide families do not map to the receptors in a simple way.
nociceptin [ N-OFQ peptide,nociceptin-orphanin FQ,orphanin FQ ] a 17-amino acid-long peptide from rat brain; resembles dynorphin A; an endogenous agonist of the opioid receptor-like ORL1 receptor; amino acid sequence given in first & second source; GenBank AF34832
