title: Stress increases descending inhibition in mouse and human colon.
abstract: BACKGROUND
  A relationship between stress and the symptoms of irritable bowel syndrome (IBS) has been well established but the cellular mechanisms are poorly understood. Therefore, we investigated effects of stress and stress hormones on colonic descending inhibition and transit in mouse models and human tissues.
  
  
  METHODS
  Stress was applied using water avoidance stress (WAS) in the animal model or mimicked using stress hormones, adrenaline (5 nM), and corticosterone (1 μM). Intracellular recordings were obtained from colonic circular smooth muscle cells in isolated smooth muscle/myenteric plexus preparations and the inhibitory junction potential (IJP) was elicited by nerve stimulation or balloon distension oral to the site of recording.
  
  
  RESULTS
  Water avoidance stress increased the number of fecal pellets compared to control (p < 0.05). WAS also caused a significant increase in IJP amplitude following balloon distension. Stress hormones also increased the IJP amplitude following nerve stimulation and balloon distension (p < 0.05) in control mice but had no effect in colons from stressed mice. No differences were observed with application of ATP between stress and control tissues, suggesting the actions of stress hormones were presynaptic. Stress hormones had a large effect in the nerve stimulated IJP in human colon (increased >50%). Immunohistochemical studies identified alpha and beta adrenergic receptor immunoreactivity on myenteric neurons in human colon.
  
  
  CONCLUSIONS
  These studies suggest that WAS and stress hormones can signal via myenteric neurons to increase inhibitory neuromuscular transmission. This could lead to greater descending relaxation, decreased transit time, and subsequent diarrhea.
authors.affiliation: GI Diseases Research Unit, Queen's University, Kingston, ON, Canada.
authors.forename: D E
authors.initials: DE
authors.lastname: Reed
authors.affiliation: GI Diseases Research Unit, Queen's University, Kingston, ON, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: GI Diseases Research Unit, Queen's University, Kingston, ON, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: Beyak
authors.affiliation: GI Diseases Research Unit, Queen's University, Kingston, ON, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Lourenssen
authors.affiliation: GI Diseases Research Unit, Queen's University, Kingston, ON, Canada.
authors.forename: M G
authors.initials: MG
authors.lastname: Blennerhassett
authors.affiliation: GI Diseases Research Unit, Queen's University, Kingston, ON, Canada.
authors.forename: W G
authors.initials: WG
authors.lastname: Paterson
authors.affiliation: GI Diseases Research Unit, Queen's University, Kingston, ON, Canada.
authors.forename: S J
authors.initials: SJ
authors.lastname: Vanner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D003106:Colon / Q000503:physiopathology*; D004594:Electrophysiology; D005260:Female; D005769:Gastrointestinal Motility / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D043183:Irritable Bowel Syndrome / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D009130:Muscle, Smooth / Q000503:physiopathology; D009197:Myenteric Plexus / Q000503:physiopathology; D009433:Neural Inhibition / Q000502:physiology; D013315:Stress, Psychological / Q000150:complications / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000502:physiology
keywords: human colon; inhibitory junction potential; motility; stress