title: Interaction of p-nitrophenylalanine enkephalins with mu-, delta- and kappa-subtypes of the opiate receptor.
abstract: Substitution of L-p-nitrophenylalanine for phenylalanine in position 4 of [D-Ala2, KLeu-NH2(5)]enkephalin analogues increased their affinity for mu-, delta- and kappa-binding sites in guinea-pig brain, increased their potency to inhibit electrically evoked contractions of the guinea-pig ileum and mouse vas deferens, and increased their analgesic potency in the mouse tail flick test, Introduction of L-adamantylalanine, but not of L-neopentylglycine, in position 5 resulted in a loss of activity.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001923:Brain Chemistry; D004723:Endorphins / Q000378:metabolism*; D004745:Enkephalins / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D011957:Receptors, Opioid / Q000378:metabolism*; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D013329:Structure-Activity Relationship
chemical_list: D004723:Endorphins; D004745:Enkephalins; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu