Study on measurement of internal anal sphincter (IAS)
movement in dogs (application as evaluation method
on defecation disorder) -the 3rd report○ Kazuaki Sasaki, Yasuyuki Ootsuka, Hirohiko Akahoshi, Kousuke Morizumi,Seiichi Katayama, Katsuhide Nishi

Objective
The number of potential fecal incontinence patient in Japan is estimated to beabout 5 million, but no fundamental treatment has been developed so far.
Therefore, development of new treatments and /or novel drugs is expected.
Screening using animal models is important for development of new therapeuticagents. In the present study, we developed a method for measuring the internaland sphincter (IAS) contractile activity in dogs under sedation. The dog fecal
incontinence model was created by impairing IAS. The contractile activity wasmeasured by manometry using a pressure sensor catheter. By periodicallymeasuring the IAS contractile activity before and after the model creation in thismodel, we obtained basic data of the contractile activity during the process of
spontaneous healing, and we also investigated the effects of a comparative control
substance, phenylephrine, aimed for the future evaluation of the efficacy of new drugs.

Summary in Japanese

わが国の便失禁の潜在患者数はおよそ500万人程度になると推定されているが、現状、根本的な治療法は開発されておらず、新たな治療法及び治療薬の開発が望まれている。新たな治療薬の開発には、モデル動物を用いたスクリーニングが重要である。そこで我々はフォーストランスデューサーを内肛門括約筋に留置し、収縮運動をテレメトリー方式で取得する方法により、無麻酔無拘束下のイヌを用いた内肛門括約筋収縮運動測定法を立ち上げ、第91 回及び第92 回日本薬理学会年会で発表した。今回我々は、内肛門括約筋に障害を負わせることで排便障害モデルを作製し、圧センサーカテーテルを用いたマノメトリー法にて内肛門括約筋の収縮運動を測定し、鎮静下でのイヌを用いて内肛門括約筋収縮運動測定法を立ち上げた。モデル作成前及び作成後の内肛門括約筋収縮運動を定期的に測定することで、自然治癒の過程での内肛門括約筋収縮運動を測定し基礎データを取得した．また、薬物の作用を評価するにあたり、比較対照物質（フェニレフリン塩酸塩）の検討も実施したので報告する。

Materials and Methods● AnimalBeagle dog，6 males，17-32 month-old● Preparation of dog fecal incontinence model
Under anesthesia, the internal anal sphincter was dissected, cauterized with an electric
scalpel, and crushed with forceps to damage the muscle tissue and reducing its
contractile function. The upper and lower parts (approximately 2×2 cm) of the internal
anal sphincter were targeted to dissect, cauterize and crush.
● Equipment

Equipment

Millar Mikro-Tip Catheter
Transducer control unit
Power Lab
Data analysis software
Automatic extraction device

Model

Manufacturer

MPR-500
TCB-510
ML846
Lab Chart Pro
Pro filometer 1725

MillarMillarADInsturments
ADInsturments
Life-Tec Inc.

The dog fecal incontinence model
was created by impairing IAS.

● Study schedule● Experimental design
Saline (N=6), 5 mL/body, Rectal administration
Phenylephrine 0.5 mg/body (N=6), 5 mL/body, Rectal administration

measurement:● Evaluation Items
Area (mmHg·15sec), and Peak (mmHg·15sec) of Internal anal sphincter contraction
waveform

Repeat before surgery and 2, 3, 4, and 5 weeks after surgery

Pre15min

30min

Rectal administration

45min

60min

Results
Effects of of phenylephrine on contraction
response of IAS before surgery

Fig. 1

Fig. 2

AUC (mmHg·15sec)

250

Peak (%)

40

403020150
100

1000-10Saline

50

2010Phenylephrine

-10

#-20

Pre15 min-40

30 min 45 min 60 min

Mean±S.D.

#-20-30-300

AUC (%)

5030200

Fig. 3

The % changes over time of IAS during the period of 5 weeks after surgery-40

Beforesurgery

2W

3W

4W

5W

-50

Beforesurgery

2W

3W

4W

Mean±S.E.
#: p<0.05，Significantly differentce from before surgery (Paired t-test)

5W

Typical waveform of IAS during administration of phenylephrine

B.A.

A.A. 15 min

A.A. 30 min

A.A. 45 min

A.A. 60 min
40 mmHg

Beforesurgery-10 mmHg
40 mmHg

2 weeks
after surgery

B.A.:Before administration, A.A.:After administration

Fig. 4

Accumulated value for 15-60 minutes
Peak(mmHg)

200

800

180160140120700

*
*

100**

**

**

AUC(mmHg)**** #600
500

#80**

**

４W

５W

* ##400
300

60200

40100

200-10 mmHg

Beforesurgery2W

3W

４W

５W

Saline0Beforesurgery

2W

Phenylephrine

3W

Mean±S.E.
*: p<0.05，**: p<0.01, Significant difference from saline (Studentʻs t-test or Aspin-Welch’s t-test)#: p<0.05，##: p<0.01, Significant difference from before surgery (Paired t-test)

Conclusion
Using an animal model of fecal incontinence in which the internal anal
sphincter was injured, the contractile force of the internal anal
sphincter was measured up to 5 weeks after surgery.
The contractile force of the internal anal sphincter muscle significantly
decreased at two weeks after surgery and then gradually recovered up
to 5 weeks (Fig. 2).
Phenylephrine administration consistently increased the contractile
force from before surgery to 5 weeks after surgery compared to thecontrol group, though the force significantly decreased two weeks aftersurgery compared to before surgery (Fig. 4).
Based on these results, it is suggested that this model can be used toevaluate the contraction response of the internal anal sphincter indogs.