title: Pharmacological modulation of rectal tone alters perception of distention in humans.
abstract: OBJECTIVE
  Drugs can alter perception of balloon distention of the GI tract. It has been proposed that the mechanism by which this occurs is through effects on visceral afferent pathways. Our hypothesis was that modulation of rectal tone will also influence the perception of rectal balloon distention.
  
  
  METHODS
  Fasting and postprandial rectal tone, compliance, and perception of rectal distention were measured in 25 healthy subjects, using a five-armed, parallel, single-blinded study design. Each subject received either glucagon, nitroglycerin, clonidine, yohimbine, or saline.
  
  
  RESULTS
  Rectal tone, but not compliance, influenced perception as measured by balloon distention of the rectum (r = 0.6, p = 0.002). Glucagon, nitroglycerin, and clonidine reduced and yohimbine increased fasting tone compared with saline. Compliance and postprandial tone were similar in all groups. Yohimbine increased rectal perception of distention.
  
  
  CONCLUSIONS
  Tone is one of the factors that influences the sensory perception of balloon distention in the human rectum. Alpha2-adrenergic agents, a nitric oxide donor, and glucagon altered fasting rectal tone, but postprandial tone was similar after administration of each agent.
authors.affiliation: Gastroenterology Research Unit, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: A
authors.initials: A
authors.lastname: Malcolm
authors.forename: S F
authors.initials: SF
authors.lastname: Phillips
authors.forename: M
authors.initials: M
authors.lastname: Camilleri
authors.forename: R B
authors.initials: RB
authors.lastname: Hanson
mesh_terms: D000328:Adult; D002404:Catheterization / Q000295:instrumentation; D005215:Fasting / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008365:Manometry / Q000295:instrumentation; D009129:Muscle Tonus / Q000187:drug effects* / Q000502:physiology; D010147:Pain Measurement; D010465:Perception / Q000187:drug effects* / Q000502:physiology; D016684:Prone Position / Q000502:physiology; D012007:Rectum / Q000187:drug effects* / Q000502:physiology; D012016:Reference Values; D016037:Single-Blind Method