Korean J Obstet Gynecol.  2012 Sep;55(9):629-635. 10.5468/KJOG.2012.55.9.629.

Clostridium botulinum toxin A significantly inhibits uterine contractions in rats undergoing mifepristone-induced preterm labor

• Jang HY
• Lee KM
• Park YS
• Moon MJ
• Hahn WB
• Ahn EH

• KMID: 2274134
• DOI: http://doi.org/10.5468/KJOG.2012.55.9.629

Abstract

OBJECTIVE
We investigated the in vivo tocolytic effect of Clostridium botulinum toxin A (BoNT/A) on mifepristone-induced preterm labor in rats.
METHODS
On day 17 of gestation, an incision was made to expose the uterus, and BoNT/A (normal saline or 20 units) was injected into the uterine horns. On day 18, mifepristone was used to induce uterine contractions. Electrical activity of uterine contractions was measured via electromyography on day 19.
RESULTS
In rats treated with 20 units of BoNT/A, the amplitude of uterine contractions was significantly decreased by 45.2 +/- 18.4 (P<0.05) from baseline, respectively. The total duration of uterine contractions was significantly decreased by 51.7 +/- 7.9 (P<0.01), respectively. The frequency of contraction bursts after treatment with 20 units of BoNT/A was decreased by 5.6 +/- 16.3 from the baseline (P=0.4).
CONCLUSION
In rats undergoing mifepristone-induced preterm labor, BoNT/A significantly inhibited uterine contractility. The decrease in uterine activity was mainly caused by a decline in the duration and intensity rather than frequency of uterine contractions.

Keyword

Clostridium botulinum toxin A; Tocolytics; Preterm labor; Mifepristone; Rat

MeSH Terms

Animals
Clostridium
Clostridium botulinum
Contracts
Electromyography
Female
Horns
Mifepristone
Obstetric Labor, Premature
Pregnancy
Rats
Tocolytic Agents
Uterine Contraction
Uterus
Mifepristone
Tocolytic Agents

Figure

• 

  Fig. 1 Injection sites (white arrows) on the left side of the uterine horn.

• 

  Fig. 2 Raw data samples of electromyography (EMG) recordings within a 5-min period from the abdominal surfaces of pregnant rats on day 19 of gestation. (A) An EMG recording from a rat in the sham-operated group (group A). Uterine EMG activity was characterized by regular, higher amplitude, and longer duration bursts of action potentials compared to animals treated with BoNT/A. (B) EMG recordings from a rat in the 20-U (group B) group, respectively. Note that the intensity and duration of uterine electrical activity were notably decreased in these groups compared with the sham-operated group.

• 

  Fig. 3 The relationship between the concentration of BoNT/A and its effects (amplitude, duration of bursts, and frequency) within a 10-min period on uterine myometrium as evaluated by abdominal surface electromyography. Results are marked with one asterisk a) if P<0.05 and two b) if P<0.01. U, units of BoNT/A injected to both uterine horns. (A) Amplitude of bursts. Increasing the concentration to 20 U of BoNT/A significantly decreased the amplitude of bursts by 45.2%±18.4% (P<0.05) compared to that of the sham-operated group. (B) Duration of bursts. Increasing the concentrations to 20 U of BoNT/A significantly shortened the duration of bursts by 51.6%±7.9% (P<0.01), respectively. (C) Frequency of bursts. Although increasing the concentration to 20 U of BoNT/A decreased the number of bursts by 5.6%±16.3% from baseline, this decrease was not statistically significant (P=0.4). BoNT/A, Clostridium botulinum toxin A.

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