title: Intestinal glucose-induced calcium-calmodulin kinase signaling in the gut-brain axis in awake rats.
abstract: BACKGROUND
  Lumenal glucose initiates changes in gastrointestinal (GI) function, including inhibition of gastric emptying, stimulation of pancreatic exocrine and endocrine secretion, and intestinal fluid secretion. Glucose stimulates the release of GI hormones and 5-hydroxytryptamine (5-HT), and activates intrinsic and extrinsic neuronal pathways to initiate changes in GI function. The precise mechanisms involved in luminal glucose-sensing are not clear; studying gut endocrine cells is difficult due to their sparse and irregular localization within the epithelium.
  
  
  METHODS
  Here we show a technique to determine activation of gut epithelial cells and the gut-brain pathway in vivo in rats using immunohistochemical detection of the activated, phosphorylated, form of calcium-calmodulin kinase II (pCaMKII).
  
  
  RESULTS
  Perfusion of the gut with glucose (60 mg) increased pCaMKII immunoreactivity in 5-HT-expressing enterochromaffin (EC) cells, cytokeratin-18 immunopositive brush cells, but not in enterocytes or cholecystokinin-expressing cells. Lumenal glucose increased pCaMKII in neurons in the myenteric plexus and nodose ganglion, nucleus of the solitary tract, dorsal motor nucleus of the vagus and the arcuate nucleus. pCaMKII expression in neurons, but not in EC cells, was significantly attenuated by pretreatment with the 5-HT(3) R antagonist ondansetron. Deoxynojirimycin, a selective agonist for the putative glucose sensor, sodium-glucose cotransporter-3 (SGLT-3), mimicked the effects of glucose with increased pCaMKII in ECs and neurons; galactose had no effect.
  
  
  CONCLUSIONS
  The data suggest that native EC cells in situ respond to glucose, possibly via SGLT-3, to activate intrinsic and extrinsic neurons and thereby regulate GI function.
authors.affiliation: Department of Anatomy, Physiology, and Cell Biology, University of California Davis School of Veterinary Medicine, Davis, CA 95616, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Vincent
authors.forename: J W
authors.initials: JW
authors.lastname: Sharp
authors.forename: H E
authors.initials: HE
authors.lastname: Raybould
mesh_terms: D017485:1-Deoxynojirimycin / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000502:physiology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000187:drug effects / Q000502:physiology*; D003243:Consciousness / Q000502:physiology*; D004759:Enterochromaffin Cells / Q000166:cytology / Q000502:physiology; D041981:Gastrointestinal Tract / Q000502:physiology*; D005944:Glucosamine / Q000031:analogs & derivatives / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000166:cytology / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D009197:Myenteric Plexus / Q000502:physiology; D017294:Ondansetron / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044406:Receptors, Serotonin, 5-HT3 / Q000187:drug effects / Q000502:physiology; D012702:Serotonin Antagonists / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D051247:Sodium-Glucose Transport Proteins / Q000187:drug effects / Q000502:physiology
chemical_list: D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists; D051247:Sodium-Glucose Transport Proteins; C501633:deoxynojirimycine; D017485:1-Deoxynojirimycin; D017294:Ondansetron; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D005947:Glucose; D005944:Glucosamine