Nociceptin is a 17 amino acid neuropeptide involved in a variety of biological systems including pain, memory, stress responses, anxiety, locomotion, and feeding behavior. It is an endogenous ligand of the NOP1 (ORL1) receptor (Ki = 88 μM in CHO cells) and, though an opioid-related peptide, does not interact directly at the classic μ-, κ-, or δ-opioid receptors.
