title: Neurogenic pathways mediating ascending and descending reflexes at the porcine ileocolonic junction.
abstract: We studied the pharmacology of the neural pathways mediating the responses of ileo- and coloileo-colonic junction (ICJ) to regional distension in ten anaesthetized pigs. Using manometric pullthroughs and a sleeve sensor, we found the ICJ demonstrated sustained tone that was resistant to tetrodotoxin. Ileal distension decreased ICJ pressure by 22.2 ¿ 10.1% (11.9 ¿ 2.7-10.1 ¿ 2.6 mmHg; P=0.002) and colonic distension augmented ICJ pressure by 23.5 ¿ 8.6% (12.8 ¿ 1.5-15.6 ¿ 2.1 mmHg; P=0.02). Bethanecol and Nw-nitro-L-arginine methyl ester (L-NAME) increased ICJ pressure (P=0.002, P=0.01, respectively). Sodium nitroprusside and isoproterenol reduced ICJ pressure (P=0.004, P=0.02, respectively). In the presence of L-NAME, the early inhibitory ileo-ICJ response was abolished, while early and late inhibitory responses were abolished by further addition of propranolol but not by the addition of hexamethonium, atropine, prazosin or yohimbine. The excitatory colo-ICJ response was replaced by inhibition in the presence of L-NAME. We concluded that: (1) the porcine ICJ displays myogenic tone which is influenced by excitatory muscarinic and inhibitory nitrergic and beta adrenergic pathways (2) an inhibitory ileo-sphincteric reflex mediated by nitrergic and beta adrenergic postganglionic neural pathways (3) both excitatory and inhibitory neurogenic colo-sphincteric reflexes exist, and the excitatory pathway involves nitrergic neurotransmission.
authors.affiliation: Department of Gastroenterology, St. George's Hospital, University of New South Wales, Sydney, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Kajimoto
authors.forename: P G
authors.initials: PG
authors.lastname: Dinning
authors.forename: D B
authors.initials: DB
authors.lastname: Gibb
authors.forename: D J
authors.initials: DJ
authors.lastname: de Carle
authors.forename: I J
authors.initials: IJ
authors.lastname: Cook
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004837:Epinephrine / Q000502:physiology; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D018738:Hexamethonium / Q000494:pharmacology; D007080:Ileocecal Valve / Q000294:innervation*; D007545:Isoproterenol / Q000494:pharmacology; D008365:Manometry; D018721:Muscarinic Agonists / Q000494:pharmacology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D018722:Nicotinic Agonists / Q000494:pharmacology; D018733:Nicotinic Antagonists / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology; D009599:Nitroprusside / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011312:Pressure; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D013045:Species Specificity; D013552:Swine / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D018721:Muscarinic Agonists; D018722:Nicotinic Agonists; D018733:Nicotinic Antagonists; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D011976:Receptors, Muscarinic; D018723:Bethanechol; D009599:Nitroprusside; D015016:Yohimbine; D009569:Nitric Oxide; D018738:Hexamethonium; D013779:Tetrodotoxin; D004246:Dimethylphenylpiperazinium Iodide; D011433:Propranolol; D007545:Isoproterenol; D019331:NG-Nitroarginine Methyl Ester; D011224:Prazosin; D004837:Epinephrine