title: In vitro profile of some opioid pentapeptide analogues.
abstract: The opiate agonist potency of thirteen synthetic enkephalin pentapeptides has been examined on the electrically stimulated guinea pig ileum and mouse vas deferens preparations in comparison with methionine and leucine enkephalins, beta-endorphin and normorphine. Their antagonism by naloxone (Ke) was also assessed on each preparation. Our findings are compatible with, and are discussed in the context of, the hypothesis that these preparations possess at least two populations of receptors.
mesh_terms: D000818:Animals; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D014649:Vas Deferens / Q000187:drug effects
chemical_list: D004723:Endorphins; D004745:Enkephalins; D009270:Naloxone