title: Weakening of naloxone antagonism in vitro and in vivo with octreotide (SMS 201-995).
abstract: Octreotide, a potent long-acting somatostatin analogue, has been shown to have a wide range of physiological actions. We have demonstrated a somatostatin-like inhibition of the electrically evoked contractions of the mouse vas deferens and an opioid antagonistic property in the same tissue. In addition, pretreatment with octreotide reduced the potency of naloxone antagonism in vitro in the mouse vas deferens and in vivo in the mouse charcoal meal test. The latter effect suggests that the agonist receptor interactions are taking place on sites allosteric to the agonist site and that the conventionally accepted concept of opioid antagonism may have to be modified.
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002606:Charcoal; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009130:Muscle, Smooth / Q000187:drug effects; D009270:Naloxone / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D009292:Narcotic Antagonists; D015282:Octreotide; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D000970:Antineoplastic Agents; D009292:Narcotic Antagonists; D002606:Charcoal; D009270:Naloxone; D013004:Somatostatin; D015282:Octreotide