title: Inhibitory motor innervation of the gall bladder musculature by intrinsic neurones containing nitric oxide in the Australian brush-tailed possum (Trichosurus vulpecula).
abstract: BACKGROUND
  Gall bladder functions are modulated by neurones intrinsic to the organ. Data are available on the neurochemical composition of intrinsic and extrinsic nerves innervating the gall bladder but are lacking on specific functional classes of gall bladder neurones.
  
  
  OBJECTIVE
  To characterise the intrinsic motor neurones of the gall bladder and identify their roles using pharmacological techniques.
  
  
  METHODS
  Retrograde tracing from the possum gall bladder muscle in vitro allowed identification of intrinsic motor neurones. Subsequently, their content of choline acetyltransferase and nitric oxide synthase, markers of acetylcholine and nitric oxide containing neurones, was established using immunohistochemical techniques. Organ bath pharmacology was used to evaluate neurotransmission by acetylcholine and nitric oxide in gall bladder muscle strips.
  
  
  RESULTS
  Innervation of the gall bladder musculature by neurones of both the muscular and serosal plexuses was demonstrated. A large proportion (62%) of these motor neurones were immunoreactive for nitric oxide synthase. All gall bladder neurones showed immunoreactivity for choline acetyltransferase. Organ bath pharmacology confirmed the neuroanatomical data, showing acetylcholine and nitric oxide mediating neurotransmission to the gall bladder musculature.
  
  
  CONCLUSIONS
  Neurones containing acetylcholine and nitric oxide, located within the muscular and serosal plexuses, provide excitatory and inhibitory motor innervation of the gall bladder, respectively. The large inhibitory innervation suggests active relaxation of the gall bladder during filling, mediated by intrinsic nerves.
authors.affiliation: Department of General and Digestive Surgery, Centre for Digestive Health and Centre for Neuroscience, Flinders University of South Australia, Flinders Medical Centre, Bedford Park, Adelaide, SA 5042, Australia. adrian.meedeniya@flinders.edu.au
authors.forename: A C
authors.initials: AC
authors.lastname: Meedeniya
authors.forename: B O
authors.initials: BO
authors.lastname: Al-Jiffry
authors.forename: H
authors.initials: H
authors.lastname: Konomi
authors.forename: A C
authors.initials: AC
authors.lastname: Schloithe
authors.forename: J
authors.initials: J
authors.lastname: Toouli
authors.forename: G T
authors.initials: GT
authors.lastname: Saccone
mesh_terms: D000818:Animals; D002795:Choline O-Acetyltransferase / Q000032:analysis; D005704:Gallbladder / Q000294:innervation*; D009474:Neurons / Q000737:chemistry*; D009569:Nitric Oxide / Q000032:analysis*; D019001:Nitric Oxide Synthase / Q000032:analysis; D009893:Opossums / Q000033:anatomy & histology*
chemical_list: D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D002795:Choline O-Acetyltransferase