Characterization of special propulsive contractions during rectal evacuation in a canine model of intestinal extrinsic denervation and rectal transection.
OBJECTIVE
The mechanism for the initiation of giant migrating contractions (GMCs) associated with defecation is not well known. The aim of this study was to describe the characteristics of special propulsive contractions (SPCs), such as GMCs, during evacuation in four experimental dog models, with emphasis on denervation.


METHODS
Twenty healthy dogs were used in this study, and they were divided into four groups, i.e., control (underwent force transducer implantation alone), denervation (underwent transection of the descending nerve fibers along the caudal mesenteric artery (CMA)), transection (underwent transection of the rectum, which corresponds to transection of the enteric nerve fibers), and denervation-plus-transection (underwent transection of the descending nerve fibers along the CMA and transection of the rectum). Colonic contractile activities were continuously recorded on a computer. Five force transducers were implanted at the serosal surfaces of the colon (C1-R). The consistency of dog feces was checked daily. The parameters of rectal relaxation (RR), defecation characteristics, and SPCs, such as motility index (MI), duration, and frequency, were measured.


RESULTS
In the control and denervation groups, GMCs were observed with evacuation, and RR occurred synchronously with the initiation of GMCs. On the other hand, in the transection and denervation-plus-transection groups, strong force contractions without RR occurred only during evacuation. The MI and duration of the transection and denervation-plus-transection groups were higher than those of other groups (p < 0.05). The frequency of SPCs was the highest in the denervation-plus-transection group.


CONCLUSIONS
In conclusion, the continuity of enteric nerves is necessary for the occurrence of GMCs and rectal relaxation (RR).
Tabe
Yuichi
Y
Department of General Surgical Science and the 21st Century COE Program, Gunma University Graduate School of Medicine, Maebashi, Japan. ytabe@med.gunma-u.ac.jp
Mochiki
Erito
E
Yanai
Mitsuhiro
M
Toyomasu
Yoshitaka
Y
Ando
Hiroyuki
H
Ohno
Tetsuro
T
Yamauchi
Hayato
H
Fukasawa
Takaharu
T
Yamaguchi
Satoru
S
Tsutsumi
Soichi
S
Asao
Takayuki
T
Kuwano
Hiroyuki
H
D000818:Animals; D003672:Defecation / Q000502:physiology*; D003714:Denervation; D004195:Disease Models, Animal; D004285:Dogs; D007422:Intestines / Q000503:physiopathology*; D009119:Muscle Contraction / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology; D012007:Rectum / Q000293:injuries* / Q000294:innervation* / Q000503:physiopathology