title: Substance P stimulates sphincter of Oddi motility and inhibits trans-sphincteric flow in the Australian brush-tailed possum.
abstract: Substance P containing nerves are widely distributed throughout the gastrointestinal tract. The aims of this study were to determine the distribution of substance P containing nerves in the extrahepatic biliary tree of the Australian brush-tailed possum and to characterize the effect of exogenous substance P on the sphincter of Oddi (SO) motility and transphincteric flow in vivo. Immunohistochemical staining of fixed specimens (n = 8) found moderate numbers of substance P containing nerve cell bodies and fibres throughout the neural plexuses of the SO, in particular in the serosal and intraluminal nerve trunks of the SO and gallbladder. Synthetic porcine substance P (1-2000 ng kg-1), administered by close intra-arterial injection (i.a.; n = 7), produced a dose-dependent elevation in basal pressure [P < 0.01] and an associated dose-dependent reduction in trans-sphincteric flow [P < 0.0001]. Substance P had no significant dose-dependent effect on SO phasic contraction amplitude or frequency. Tetrodotoxin (9 micrograms kg-1, i.a.) did not inhibit the effect of substance P on SO motility and trans-sphincteric flow (n = 5). In conclusion, substance P containing nerves are found throughout the possum extrahepatic biliary tree. Exogenous substance P stimulates SO motility and reduces trans-sphincteric flow in vivo by acting directly on the sphincter smooth muscle.
authors.affiliation: Department of Surgery, Flinders University, Flinders Medical Centre, Adelaide, Australia.
authors.forename: M R
authors.initials: MR
authors.lastname: Cox
authors.forename: R T
authors.initials: RT
authors.lastname: Padbury
authors.forename: J R
authors.initials: JR
authors.lastname: Harvey
authors.forename: R A
authors.initials: RA
authors.lastname: Baker
authors.forename: J
authors.initials: J
authors.lastname: Toouli
authors.forename: G T
authors.initials: GT
authors.lastname: Saccone
mesh_terms: D000818:Animals; D001315:Australia; D001646:Bile / Q000378:metabolism*; D016473:Gallbladder Emptying / Q000187:drug effects* / Q000502:physiology; D007269:Injections, Intra-Arterial; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009893:Opossums; D009803:Sphincter of Oddi / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D013373:Substance P / Q000008:administration & dosage / Q000494:pharmacology*; D013552:Swine
chemical_list: D013373:Substance P