Effects of sphincterotomy and pudendal nerve transection on the anal sphincter in a rat model.
OBJECTIVE
Our objective was to define anal resting pressure and electromyography of the normal rat anal sphincter and investigate the short-term effects of both mechanical trauma to the anal sphincter muscles and pudendal nerve transection.


METHODS
Forty-five virgin female Sprague-Dawley rats were randomly allotted to three groups: controls (n = 21), sphincterotomy (n = 12), and pudendal nerve transection (n = 12). Anal pressure was monitored using a saline-filled balloon connected to a pressure transducer. Anal pressure and electromyography of the anal sphincter with use of a needle electrode were recorded both before and after injury or succinylcholine administration.


RESULTS
Anal pressure data were consistent with rhythmic pressure contractions. Succinylcholine significantly reduced both pressure and electromyography signals. Electromyography amplitude and frequency decreased after nerve transection but not after sphincterotomy. The histology showed that the rat anal anatomy has muscular components that compare with human anatomy. The sphincterotomy group showed injury to the anal sphincters and the sphincter anatomy of the nerve transection group appeared similar to the control group. The anal pressure wave appears to be created by synergistic activity of both striated and smooth muscle of the anal sphincter.


CONCLUSIONS
The female rat is a suitable and reliable model for studying effect of direct and indirect injury to the anal sphincters.
Zutshi
Massarat
M
Department of Colorectal Surgery, Cleveland Clinic, Cleveland, Ohio, USA. zutshim@ccf.org
Salcedo
Levilester B
LB
Zaszczurynski
Paul J
PJ
Hull
Tracy L
TL
Butler
Robert S
RS
Damaser
Margot S
MS
D000200:Action Potentials / Q000502:physiology; D001003:Anal Canal / Q000293:injuries* / Q000294:innervation / Q000601:surgery*; D000818:Animals; D004195:Disease Models, Animal; D004576:Electromyography; D005260:Female; D009119:Muscle Contraction / Q000502:physiology; D053580:Muscle Strength; D054792:Muscle, Striated / Q000294:innervation* / Q000503:physiopathology* / Q000601:surgery; D011312:Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results