Nociceptin
endogenous
What it isEndogenous peptide at the opioid-related NOP receptor.
Why this oneNOP signaling modulates the reward and tolerance produced by classical opioids, which is why NOP-mu ligands are pursued.
What limits itIt is not analgesic in the classical sense and can oppose mu analgesia supraspinally.
NO BOXED WARNINGS
Principal riskNo approved drug targets it yet; effects differ between spinal and supraspinal sites