title: Pharmacologic characterization of intrinsic mechanisms controlling tone and relaxation of porcine lower esophageal sphincter.
abstract: The neurotransmitters mediating relaxation of lower esophageal sphincter (LES) were studied using circular LES strips from adult pigs in organ baths. LES relaxation by sodium nitroprusside (1 nM-3 microM), vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP; 1 nM-1 microM), ATP (10 microM-30 mM), and tricarbonyldichlororuthenum dimer (1 microM-1 mM) was unaffected by tetrodotoxin (1 microM) or l-N(G)-nitroarginine methyl ester (l-NAME; 100 microM). Calcitonin gene-related peptide (CGRP; 1 nM-1 microM) did not affect LES tone. ATP relaxation was blocked by 1 microM apamin and the P2Y(1) antagonist MRS 2179 (N6-methyl 2'-deoxyadenosine 3',5'-bisphosphate; 10 microM). Apamin inhibited PACAP relaxation. VIP and PACAP relaxation was blocked by 10 U/ml alpha-chymotrypsin. L-NAME (-62.52 +/- 13.13%) and 1H-[1,2,4]oxadiazole-[4,3-alpha]quinoxalin-1-one (ODQ; 10 microM, -67.67 +/- 6.80%) similarly inhibited electrical LES relaxation, and apamin blocked non-nitrergic relaxation. Nicotine relaxation (100 microM) was inhibited by L-NAME (-60.37 +/- 10.8%) and ODQ (-41.90 +/- 7.89%), and apamin also blocked non-nitrergic relaxation. Non-nitrergic and apamin-sensitive LES relaxation by electrical stimulation or nicotine was strongly inhibited by MRS 2179, slightly inhibited by alpha-chymotrypsin and the P2X(1,2,3) receptor antagonist NF 279 (8,8 cent-[carbonylbis(imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino)]bis-1,3,5-naphthalenetrisulfonic acid hexasodium salt; 10 microM), and unaffected by tin protoporphyrin IX (100 microM). Porcine LES relaxation after stimulation of intrinsic inhibitory motor neurons is mediated by two main neuromuscular pathways: nitric oxide through guanylate cyclase signaling and apamin-insensitive mechanisms and by non-nitrergic apamin-sensitive neurotransmission mainly mediated by ATP, ADP, or a related purine acting on P2Y1 receptors and a minor contribution of purinergic P2X1,2,3 receptors and PACAP. Nitrergic and purinergic co-transmitters show parallel effects of similar magnitude without major interplay. Our study shows no role for CGRP and only a minor one for VIP and carbon monoxide in porcine LES relaxation.
authors.affiliation: Fundació de Gastroenterologia Dr. Francisco Vilardell, Barcelona, Spain.
authors.forename: Ricard
authors.initials: R
authors.lastname: Farré
authors.forename: Mariona
authors.initials: M
authors.lastname: Aulí
authors.forename: Begoña
authors.initials: B
authors.lastname: Lecea
authors.forename: Emma
authors.initials: E
authors.lastname: Martínez
authors.forename: Pere
authors.initials: P
authors.lastname: Clavé
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D004558:Electric Stimulation; D049630:Esophageal Sphincter, Lower / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D009126:Muscle Relaxation / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009433:Neural Inhibition; D018377:Neurotransmitter Agents / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000494:pharmacology; D013552:Swine; D013873:Thionucleotides / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
chemical_list: D018377:Neurotransmitter Agents; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D013873:Thionucleotides; D009599:Nitroprusside; C030812:adenosine 5'-O-(2-thiodiphosphate); D014660:Vasoactive Intestinal Peptide; D000244:Adenosine Diphosphate; D009538:Nicotine; D000255:Adenosine Triphosphate; D015740:Calcitonin Gene-Related Peptide; D019331:NG-Nitroarginine Methyl Ester