Opioids increase potassium conductance in submucous neurones of guinea-pig caecum by activating delta-receptors.
Intracellular records were made from neurones in the submucous plexus of the guinea-pig caecum. [Met5]enkephalin, [Leu5]enkephalin, [D-Ala2,D-Leu5]enkephalin (DADLE) and [D-Ser2,Leu5]enkephalin-Thr (DSLET) hyperpolarized the membrane when applied in concentrations of 30 nm-10 microM. Normorphine, [D-Ala2, MePhe4,Gly5]enkephalin-ol (DAGO), [D-Ala2,MePhe4,Met(0)5]enkephalin-ol (FK33824), dynorphin A and tifluadom had no effect at concentrations up to 10 microM. The hyperpolarization resulted from an increase in the membrane potassium conductance. Hyperpolarizations induced by [Met5]enkephalin were antagonized competitively by naloxone and by N-bisallyl[aminoisobutyrate2,3, Leu5]enkephalin (ICI 174864). The Schild plots for these antagonisms had slopes not different from one, and the dissociation equilibrium constants among individual neurones were 5-50 nM for naloxone and 5-60 nM for ICI 174864. The results indicate that the opioid receptors on guinea-pig submucous neurones which are coupled to potassium channels are of the delta-type.
Mihara
S
S
North
R A
RA
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D002432:Cecum / Q000187:drug effects / Q000502:physiology; D004723:Endorphins / Q000494:pharmacology*; D004743:Enkephalin, Leucine / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000502:physiology*; D009431:Neural Conduction / Q000187:drug effects; D009474:Neurons / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000502:physiology*; D011957:Receptors, Opioid / Q000502:physiology*; D017465:Receptors, Opioid, delta; D013004:Somatostatin / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D004723:Endorphins; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D013004:Somatostatin; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; D011188:Potassium; D009638:Norepinephrine