title: Involvement of parasympathetic pelvic efferent pathway in psychological stress-induced defecation.
abstract: OBJECTIVE
  To investigate the role of the pelvic nerve pathway in stress-induced acceleration of colorectal transit and defecation in rats.
  
  
  METHODS
  Surgical transection of rectal nerves (rectal branches of the pelvic nerve), vagotomy (Vag) or adrenalectomy (Adx) were performed bilaterally in rats. Number of fecal pellet output of these rats was measured during 1-h water avoidance stress (WAS). To evaluate the colonic transit, rats were given phenol red through the catheter indwelled in the proximal colon and subjected to WAS. After WAS session, entire colon and rectum were isolated and distribution of phenol red was measured. Distal colonic and rectal transit was evaluated using glass bead. Rats were inserted the glass bead into the distal colon and evacuation rate of the bead was measured. Neural activation was assessed by immunohistochemical staining of c-Fos and PGP9.5 in colonic whole-mount preparations of longitudinal muscle myenteric plexus (LMMP).
  
  
  RESULTS
  In the sham-operated rats (sham op), WAS significantly increased defecation and accelerated colorectal transit with marked elevation of plasma corticosterone level. Compared with sham-operated rats, increase in the excretion of fecal pellets during WAS was significantly reduced by rectal nerve transection (RNT) (sham op: 6.9 ± 0.8 vs RNT: 4.3 ± 0.6, P < 0.05) or Vag (sham op: 6.4 ± 0.8 vs Vag: 3.7 ± 1.1, P < 0.05), although corticosterone level remained elevated. Adx-rats significantly increased the defecation despite the lower corticosterone level. Distribution pattern of phenol red showed RNT inhibited distal colonic and rectal transit accelerated by WAS, while Vag inhibited proximal colonic transit. Suppression of distal colonic and rectal transit by RNT was further confirmed by the bead evacuation rate (sham op: 80.0% vs RNT: 53.8%). WAS significantly increased the number of c-Fos-immunoreactive neural cells in the LMMP of the proximal and distal colon, whereas c-Fos expression was decreased by RNT in the distal colon (sham op: 9.0 ± 2.0 vs RNT: 4.4 ± 1.0, P < 0.05) and decreased by Vag in the proximal colon.
  
  
  CONCLUSIONS
  Pelvic nerve conveys WAS stimuli from the brain to the distal colon, and directly activate the myenteric neurons, followed by the increase of its motility.
authors.affiliation: Yakult Central Institute for Microbiological Research, Tokyo 186-8650, Japan. kazunori-suda@yakult.co.jp
authors.forename: Kazunori
authors.initials: K
authors.lastname: Suda
authors.forename: Hiromi
authors.initials: H
authors.lastname: Setoyama
authors.forename: Masanobu
authors.initials: M
authors.lastname: Nanno
authors.forename: Satoshi
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Mitsuhisa
authors.initials: M
authors.lastname: Kawai
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D003106:Colon / Q000294:innervation*; D003672:Defecation; D004195:Disease Models, Animal; D004525:Efferent Pathways / Q000503:physiopathology; D005769:Gastrointestinal Motility; D007001:Hypogastric Plexus / Q000378:metabolism / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D009197:Myenteric Plexus / Q000378:metabolism / Q000503:physiopathology; D010275:Parasympathetic Nervous System / Q000503:physiopathology* / Q000601:surgery; D010388:Pelvis / Q000294:innervation*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012007:Rectum / Q000294:innervation*; D013315:Stress, Psychological / Q000150:complications / Q000503:physiopathology*; D013997:Time Factors; D014628:Vagotomy
chemical_list: D015415:Biomarkers; D016760:Proto-Oncogene Proteins c-fos
keywords: Colonic transit; Fecal pellet output; Pelvic nerve; Psychological stress; Vagus nerve