Nociceptin/Orphanin FQ (N/OFQ), a 17 a.a. neuropeptide that is structurally related to the opioid peptide dynorphin A originates from proorphanin, a larger peptide encoded by the preproorphanin gene (Meunier et al., 1995; Reinscheid et al., 1995). N/OFQ and its receptor, NOPR, are widely expressed in the brain where they control the release of other neurotransmitters through presynaptic actions. (Darland et al., 1998; Neal et al., 1999).
