title: Regulatory role of enteric mu and kappa opioid receptors in the release of acetylcholine and norepinephrine from guinea pig ileum.
abstract: We examined the role of opioid receptor subtypes in the contraction and release of acetylcholine (ACh) and norepinephrine in longitudinal muscle-myenteric plexus preparations of the guinea pig ileum. [D-Ala2, N-Me-Phe4, Gly5-ol]enkephalin (DAMGO) (10(-8) to 10(-5) M) inhibited the contraction and the release of ACh evoked by 0.2 and 1 Hz of electrical stimulation (ES), whereas the response to 5 Hz was enhanced by low concentrations of DAMGO (10(-9) to 10(-8) M) and inhibited by high concentrations (10(-7) to 10(-5) M); naloxone antagonized these effects. In preparations treated with yohimbine, DAMGO inhibited the ES (5 Hz)-evoked contraction and ACh release, but failed to enhance either effect. Dynorphin-A inhibited the contraction and ACh release evoked by 0.2, 1 and 5 Hz of ES, and the effect of dynorphin-A was mimicked by U-69593 [5 alpha,7 alpha,8 beta-(-)-N-methyl-N-[7- (pyrrolinyl)-1-ozaspiro(4,5)dec-8-yl]-benzene] and antagonized by MR 2266 [(-)-alpha-5,9-diethyl-2-(3-furylmethyl)-2'-hydroxy-6,7-benzomorphan]. The release of norepinephrine evoked by 5 Hz of ES was inhibited by DAMGO (10(-10) to 10(-6) M), but not by U-69593, and the effect of DAMGO was antagonized by naloxone. Thus, it would appear that mu-opioid receptors are present on both cholinergic and adrenergic neurons, whereas kappa-opioid receptors are present on cholinergic neurons. The affinity of DAMGO was 30 times higher for the mu-opioid receptors on the adrenergic than on the cholinergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, Kobe University School of Medicine, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Nakayama
authors.forename: K
authors.initials: K
authors.lastname: Taniyama
authors.forename: S
authors.initials: S
authors.lastname: Matsuyama
authors.forename: N
authors.initials: N
authors.lastname: Ohgushi
authors.forename: K
authors.initials: K
authors.lastname: Tsunekawa
authors.forename: C
authors.initials: C
authors.lastname: Tanaka
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000494:pharmacology; D004558:Electric Stimulation; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu
chemical_list: D004745:Enkephalins; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004399:Dynorphins; D000109:Acetylcholine; D009638:Norepinephrine