title: Effects of potential mediators of an intestinal brake mechanism on gut motility in Chinook salmon (Oncorhynchus tshawytscha).
abstract: Potential humoral factors controlling an intestinal brake mechanism in Chinook salmon were characterised in terms of their effect on frequency and amplitude of spontaneous contractions in gastrointestinal (GI) rings. Concentration-response curves of gut contractility were produced for cholecystokinin-8 (CCK-8), gastrin-1, glucagon-like peptide-1 (GLP-1) and 5-hydroxytryptamine (5-HT) using gut rings from cardiac stomach (CS), pyloric stomach (PY), pyloric sphincter (Psp) and intestine (Int). Calculated log10 molar (M) EC50 values for CCK-8 (n=7) were: CS -8.15+/-0.90, PY -7.88+/-0.48, Psp -8.98+/-0.68, Int -8.93+/-0.64. Log10 M EC50 values calculated for gastrin 1 (n=7) were: CS -12.45+/-0.66, PY -12.55+/-0.63, Psp -9.35+/-0.78, Int -12.69+/-1.12. Log10 M EC50 values calculated for 5-HT (n=6) were: CS -4.78+/-1.05 and Psp -6.18+/-1.14. GLP -1 (n=4) produced no response in any of the tissues examined. Spontaneous contractions, measured as spikes per minute and the peak force generated were also measured for each hormone-tissue combination. The Psp generated the greatest mass-specific force, with stomach rings generating the least force. Dilutions of serum from fish diagnosed with gastric dilation air sacculitis (GDAS +ve) increased gut contractility compared to controls (GDAS -ve).
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand. lgf16@student.canterbury.ac.nz
authors.forename: Leonard G
authors.initials: LG
authors.lastname: Forgan
authors.forename: Malcolm E
authors.initials: ME
authors.lastname: Forster
mesh_terms: D000818:Animals; D002299:Cardia / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005765:Gastrointestinal Agents / Q000494:pharmacology*; D005769:Gastrointestinal Motility / Q000187:drug effects* / Q000502:physiology; D052216:Glucagon-Like Peptide 1 / Q000494:pharmacology*; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000187:drug effects / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D011708:Pylorus / Q000187:drug effects / Q000502:physiology; D012474:Salmon; D012701:Serotonin / Q000494:pharmacology*; D012844:Sincalide / Q000494:pharmacology*
chemical_list: D005765:Gastrointestinal Agents; D012701:Serotonin; D052216:Glucagon-Like Peptide 1; D012844:Sincalide