title: Blockade by pertussis toxin of the opioid effect on guinea pig ileum. Contractility and electrophysiological neuronal recording.
abstract: The aim of the present study was to analyse the correlation between functional and electrophysiological effects of the opioids in guinea pig ileum. Preparations of guinea pig ileum myenteric plexus-longitudinal muscle strips were used to compare the effect of two opioids, morphine (a mu-agonist) and U-50,488H (a kappa-agonist) on the electrically-induced contractile response and the excitatory postsynaptic potentials exhibited by the myenteric neurones when the internodal strands are electrically stimulated. Both opioids dose-dependently inhibited the contractile responses and the fast excitatory postsynaptic potentials (fEPSPs) in S neurones but did not modify the amplitude of the slow postsynaptic potentials. Pertussis toxin pretreatment was able to antagonise the effects of both morphine and U-50,448H. From our results it can be suggested that the effect of the opioids on guinea pig ileum involves the inhibition of neuronal fEPSPs.
authors.affiliation: Departmento Farmacología, Facultad de Medicina, Universidad Complutense de Madrid, 28040, Madrid, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Abalo
authors.forename: D
authors.initials: D
authors.lastname: Pascual
authors.forename: C
authors.initials: C
authors.lastname: Goicoechea
authors.forename: M I
authors.initials: MI
authors.lastname: Martín
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D009020:Morphine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D037342:Pertussis Toxin; D017473:Receptors, Opioid, kappa / Q000819:agonists; D017450:Receptors, Opioid, mu / Q000819:agonists; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D009292:Narcotic Antagonists; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D010566:Virulence Factors, Bordetella; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D009020:Morphine; D037342:Pertussis Toxin