title: Establishment of a new anal sphincter injury model in rats based on cardiotoxin.
abstract: OBJECTIVE
  Mainstream models for anal sphincter injury use large animals. We developed a simple and stable anal sphincter injury model in a small animal (i.e., rats) to obtain manometry measurements by using a miniaturized probe and applying cardiotoxin.
  
  
  METHODS
  The histological structure of the anal canal was evaluated by using manometry in normal rats (n=40). We damaged the internal and external anal sphincters by locally administering snake poison (cardiotoxin; 20 uM, 100μL 8 points). We evaluated the anal canal function through manometry measurements (n=5) and examined the histology using hematoxylin-eosin staining (at each time point, n=3; total n=15).
  
  
  RESULTS
  The manometry parameters and structure of the anal canal of normal rats were similar to those of humans, because rats have resting pressure, rectoanal reflex in the manometry, and an external and internal anal sphincter. After inducing injury, the following findings were observed: rhythmic wave loss and a remarkable reduction in the anal sphincter resting pressure; and local bleeding and advanced infiltration of the inflammatory cells (day 1) and the loss of muscle fibers (day 3).
  
  
  CONCLUSIONS
  This new rat model will contribute to increasing the knowledge on the anal canal.
authors.affiliation: Department of Pediatric Surgery, Nihon University School of Medicine, Tokyo, Japan; Department of Functional Morphology, Division of Cell Regeneration and Transplantation, Nihon University School of Medicine, Tokyo, Japan. Electronic address: jikan-gensyu@hotmail.co.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hosokawa
authors.affiliation: Department of Pediatric Surgery, Nihon University School of Medicine, Tokyo, Japan; Department of Functional Morphology, Division of Cell Regeneration and Transplantation, Nihon University School of Medicine, Tokyo, Japan. Electronic address: konuma.noriyoshi@nihon-u.ac.jp.
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Konuma
authors.affiliation: Department of Surgery, Jichi Medical University, Saitama Medical Center, Saitama, Japan. Electronic address: ikeda.taro@jichi.ac.jp.
authors.forename: Taro
authors.initials: T
authors.lastname: Ikeda
authors.affiliation: Department of Pediatric Surgery, Nihon University School of Medicine, Tokyo, Japan; Department of Functional Morphology, Division of Cell Regeneration and Transplantation, Nihon University School of Medicine, Tokyo, Japan. Electronic address: monoclonal-antiboby@mail.goo.ne.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hashimoto
authors.affiliation: Department of Pediatric Surgery, Nihon University School of Medicine, Tokyo, Japan. Electronic address: kaneda.hide@nihon-u.ac.jp.
authors.forename: Hide
authors.initials: H
authors.lastname: Kaneda
authors.affiliation: Department of Pediatric Surgery, Nihon University School of Medicine, Tokyo, Japan. Electronic address: ohashi.kensuke@nihon-u.ac.jp.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Ohashi
authors.affiliation: Department of Functional Morphology, Division of Cell Regeneration and Transplantation, Nihon University School of Medicine, Tokyo, Japan. Electronic address: matsumoto.taro@nihon-u.ac.jp.
authors.forename: Taro
authors.initials: T
authors.lastname: Matsumoto
authors.affiliation: Department of Pediatric Surgery, Nihon University School of Medicine, Tokyo, Japan. Electronic address: koshinaga.tsugumichi@nihon-u.ac.jp.
authors.forename: Tsugumichi
authors.initials: T
authors.lastname: Koshinaga
mesh_terms: D001003:Anal Canal / Q000187:drug effects / Q000293:injuries* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D054715:Cardiotoxins / Q000008:administration & dosage / Q000633:toxicity*; D005260:Female; D008365:Manometry; D023421:Models, Animal; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley / Q000293:injuries* / Q000502:physiology; D012910:Snake Venoms / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D054715:Cardiotoxins; D012910:Snake Venoms
keywords: Anal sphincter injury; Anal sphincter injury model; Cardiotoxin; Manometry measurements; Prospective study; Rat model