title: Coloanal motor coordination in association with high-amplitude colonic contractions after pharmacological stimulation.
abstract: OBJECTIVE
  The rectoanal inhibitory reflex facilitates defecation by relaxation of the internal anal sphincter during rectal distention by gas or stool. Defecation is sometimes preceded by high-amplitude propagated contractions (HAPCs). Our objective was to seek evidence for motor coordination between human colonic and anal sphincter functions.
  
  
  METHODS
  As part of a study of alpha2 modulation of colonic and anal motor functions in 32 healthy volunteers, we studied the relationship between high HAPCs and anal sphincter pressure with colonic manometry, barostat, and a Dent sleeve in the anal canal.
  
  
  RESULTS
  Twenty-two HAPCs were observed; in 19/22 HAPCs there was optimal positioning of the Dent sleeve to assess the anal sphincter. Eighteen of 19 HAPCs occurred postprandially; 14 HAPCs occurred after administration of yohimbine, three after clonidine, and one before any drug administration. Seven followed experimental balloon distention. Anal sphincter relaxation occurred (14 +/- 4 s) before the recorded onset of HAPC in the descending colon and 88 +/- 7 s before the arrival of the HAPC in the rectum. After or during the HAPCs, anal sphincter pressure decreased by 40 +/- 4% and increased by 56 +/- 8% in the postrelaxation phase.
  
  
  CONCLUSIONS
  The close temporal association between anal sphincter relaxation and onset of HAPC in the descending colon suggests a coloanal reflex that may facilitate defecation during mass movements independently of the rectoanal inhibitory reflex.
authors.affiliation: Gastroenterology Research Unit, Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
authors.forename: A
authors.initials: A
authors.lastname: Malcolm
authors.forename: M
authors.initials: M
authors.lastname: Camilleri
mesh_terms: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000328:Adult; D001003:Anal Canal / Q000187:drug effects*; D003000:Clonidine; D003106:Colon / Q000187:drug effects*; D003672:Defecation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects*; D006801:Humans; D008297:Male; D008365:Manometry; D009126:Muscle Relaxation / Q000187:drug effects; D012016:Reference Values; D012018:Reflex / Q000187:drug effects; D015016:Yohimbine
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D015016:Yohimbine; D003000:Clonidine