title: Transient receptor potential ankyrin 1 is expressed by inhibitory motoneurons of the mouse intestine.
abstract: OBJECTIVE
  Transient receptor potential ankyrin (TRPA) 1, an excitatory ion channel expressed by sensory neurons, mediates somatic and visceral pain in response to direct activation or noxious mechanical stimulation. Although the intestine is routinely exposed to irritant alimentary compounds and inflammatory mediators that activate TRPA1, there is no direct evidence for functional TRPA1 receptors on enteric neurons, and the effects of TRPA1 activation on intestinal function have not been determined. We characterized expression of TRPA1 by enteric neurons and determined its involvement in the control of intestinal contractility and transit.
  
  
  METHODS
  TRPA1 expression was characterized by reverse-transcription polymerase chain reaction and immunofluorescence analyses. TRPA1 function was examined by Ca(2+) imaging and by assays of contractile activity and transit.
  
  
  RESULTS
  We detected TRPA1 messenger RNA in the mouse intestine and TRPA1 immunoreactivity in enteric neurons. The cecum and colon had immunoreactivity for neuronal TRPA1, but the duodenum did not. TRPA1 immunoreactivity was also detected in inhibitory motoneurons and descending interneurons, cholinergic neurons, and intrinsic primary afferent neurons. TRPA1 activators, including cinnamaldehyde, allyl isothiocyanate (AITC), and 4-hydroxynonenal, increased [Ca(2+)](i) in myenteric neurons. These were reduced by a TRPA1 antagonist (HC-030031) or deletion of Trpa1. TRPA1 activation inhibited contractility of the segments of colon but not stomach or small intestine of Trpa1(+/+) but not Trpa1(-/-) mice; this effect was reduced by tetrodotoxin or N(G)-nitro-l-arginine methyl ester. Administration of AITC by gavage did not alter gastric emptying or small intestinal transit, but luminal AITC inhibited colonic transit via TRPA1.
  
  
  CONCLUSIONS
  Functional TRPA1 is expressed by enteric neurons, and activation of neuronal TRPA1 inhibits spontaneous neurogenic contractions and transit of the colon.
authors.affiliation: Center for the Neurobiology of Digestive Diseases, University of California, San Francisco, San Francisco, California, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Poole
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Pelayo
authors.forename: Fiore
authors.initials: F
authors.lastname: Cattaruzza
authors.forename: Yien-Ming
authors.initials: YM
authors.lastname: Kuo
authors.forename: Gregory
authors.initials: G
authors.lastname: Gai
authors.forename: Jonathon V
authors.initials: JV
authors.lastname: Chiu
authors.forename: Romke
authors.initials: R
authors.lastname: Bron
authors.forename: John B
authors.initials: JB
authors.lastname: Furness
authors.forename: Eileen F
authors.initials: EF
authors.lastname: Grady
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Bunnett
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives / Q000494:pharmacology; D000447:Aldehydes / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002432:Cecum / Q000187:drug effects / Q000294:innervation / Q000378:metabolism / Q000502:physiology; D003106:Colon / Q000187:drug effects / Q000294:innervation / Q000378:metabolism / Q000502:physiology; D004386:Duodenum / Q000187:drug effects / Q000294:innervation / Q000378:metabolism / Q000502:physiology; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D005724:Ganglia / Q000378:metabolism; D005746:Gastric Emptying / Q000502:physiology*; D005753:Gastric Mucosa / Q000378:metabolism; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology*; D007082:Ileum / Q000187:drug effects / Q000294:innervation / Q000378:metabolism / Q000502:physiology; D007395:Interneurons / Q000187:drug effects / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D017879:Isothiocyanates / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009046:Motor Neurons / Q000187:drug effects / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013270:Stomach / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D013373:Substance P / Q000494:pharmacology; D000074025:TRPA1 Cation Channel; D050051:Transient Receptor Potential Channels / Q000819:agonists / Q000378:metabolism* / Q000502:physiology*
chemical_list: D000447:Aldehydes; D017879:Isothiocyanates; D012333:RNA, Messenger; D000074025:TRPA1 Cation Channel; D050051:Transient Receptor Potential Channels; C475685:Trpa1 protein, mouse; D013373:Substance P; D000171:Acrolein; D002217:Carbachol; C004471:allyl isothiocyanate; C027576:4-hydroxy-2-nonenal; C012843:cinnamaldehyde