title: Regional- and agonist-dependent facilitation of human neurogastrointestinal functions by motilin receptor agonists.
abstract: OBJECTIVE
  Delayed gastric emptying is poorly managed. Motilin agonists are potential treatments but inadequate understanding into how enteric nerve functions are stimulated compromises drug/dose selection. Resolution is hampered by extreme species dependency so methods were developed to study human gastrointestinal neuromuscular activities and the neurobiology of motilin.
  
  
  METHODS
  Protocols to study neuromuscular activities were developed for different regions of human stomach and intestine (71 patients) using circular muscle preparations and electrical field stimulation (EFS) of intrinsic nerves. Other tissues were fixed for immunohistochemistry.
  
  
  RESULTS
  EFS evoked contractions and/or relaxations via cholinergic and nitrergic neurons, with additional tachykinergic activity in colon; these were consistent after 154 min (longer if stored overnight). Motilin 1-300 nM and the selective motilin agonist GSK962040 0.1-30 µM acted pre-junctionally to strongly facilitate cholinergic contractions of the antrum (E(max) ≈ 1000% for motilin), with smaller increases in fundus, duodenum and ileum; high concentrations increased baseline muscle tension in fundus and small intestine. There were minimal effects in the colon. In the antrum, cholinergic facilitation by motilin faded irregularly, even with peptidase inhibitors, whereas facilitation by GSK962040 was long lasting. Motilin receptor immunoreactivity was identified in muscle and myenteric plexus predominantly in the upper gut, co-expressed with choline acetyltransferase in neurons.
  
  
  CONCLUSIONS
  Motilin and GSK962040 strongly facilitated cholinergic activity in the antrum, with lower activity in fundus and small intestine only. Facilitation by motilin was short lived, consistent with participation in migrating motor complexes. Long-lasting facilitation by GSK962040 suggests different receptor interactions and potential for clinical evaluation.
authors.affiliation: Neurogastroenterology group, Blizard Institute, Barts & The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
authors.forename: J
authors.initials: J
authors.lastname: Broad
authors.forename: S
authors.initials: S
authors.lastname: Mukherjee
authors.forename: M
authors.initials: M
authors.lastname: Samadi
authors.forename: J E
authors.initials: JE
authors.lastname: Martin
authors.forename: G E
authors.initials: GE
authors.lastname: Dukes
authors.forename: G J
authors.initials: GJ
authors.lastname: Sanger
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004558:Electric Stimulation; D005260:Female; D005769:Gastrointestinal Motility; D006801:Humans; D066298:In Vitro Techniques; D007422:Intestines / Q000187:drug effects* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009037:Motilin / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology*; D011964:Receptors, Gastrointestinal Hormone / Q000819:agonists* / Q000502:physiology; D018013:Receptors, Neuropeptide / Q000819:agonists* / Q000502:physiology; D013270:Stomach / Q000187:drug effects* / Q000502:physiology
chemical_list: C541863:N-(3-fluorophenyl)-1-((4-(((3S)-3-methyl-1-piperazinyl)methyl)phenyl)acetyl)-4-piperidinamine; D010879:Piperazines; D010880:Piperidines; D011964:Receptors, Gastrointestinal Hormone; D018013:Receptors, Neuropeptide; C050802:motilin receptor; D009037:Motilin