The recently discovered neuropeptide nociceptin was found to inhibit electrically induced contractions of the mouse vas deferens. Nociceptin and its 14-Tyr analog were each partial agonists, but with high affinity (ED50 of 20 nM). This activity was not opioid in nature, as it was not inhibited by either selective or non-selective opiate antagonists.
Animals Dose-Response Relationship, Drug