title: In vitro opioid receptor assays.
abstract: Although opioid analgesics have been used for centuries, identification of opioid receptors and the ability of an opioid receptor antagonist to block natural pain processes prompted a search for endogenous opioid peptides. In vitro models were needed to characterize opioid activity in biological samples. The longitudinal muscle/myenteric plexus (LM/MP) of the guinea pig ileum was the classical in vitro assay system, but the development of the mouse vas deferens (MVD) assay provided another important model that could be employed. Both assays entail electrical stimulation of intramural nerves to produce muscle contractions of the target organ. The robust contractions of the LM/MP are inhibited by µ and κ opioid receptor agonists, while the more labile contractions of the MVD are inhibited by µ, κ, and δ opioid receptor agonists. These in vitro assay systems are useful for evaluating biological activity of unknown substances and studying the properties of drug tolerance and both are described in this unit.
authors.affiliation: The Department of Pharmacology and Toxicology, The Brody School of Medicine at East Carolina University, Greenville, North Carolina, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Taylor
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001681:Biological Assay / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009197:Myenteric Plexus / Q000187:drug effects*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D011957:Receptors, Opioid / Q000819:agonists / Q000187:drug effects; D017465:Receptors, Opioid, delta / Q000819:agonists; D017473:Receptors, Opioid, kappa / Q000819:agonists; D017450:Receptors, Opioid, mu / Q000819:agonists
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D009020:Morphine