Inhibition of tachykinin release from peripheral endings of sensory nerves by nociceptin, a novel opioid peptide

Abstract
The novel heptadecapeptide opioid, nociceptin, produced a concentration‐dependent (EC50 28 nM) suppression of the inotropic response of the guinea‐pig isolated renal pelvis to electrical stimulation, a response mediated by release of tachykinins from sensory nerves. Nociceptin did not affect the response to neurokinin A, indicating a prejunctional site of action on tachykininergic nerves. The effect of nociceptin was unchanged in the presence of the μ, δ and ***k opioid receptor antagonists, naloxone, naltrindole and nor‐binaltorphimine.