Decreased electromechanical activity of guinea pig circular muscle during pregnancy.

BACKGROUND

Delayed gastric emptying has been reported during pregnancy; however, its underlying mechanism is poorly understood. The purpose of this study was to determine if electromechanical activity of antral circular muscle is decreased during pregnancy.

METHODS

Antral muscle strips from third-trimester pregnant and age-matched control virgin female guinea pigs were studied in vitro.

RESULTS

Spontaneous and bethanechol-induced phasic antral contractions from pregnant guinea pigs were reduced significantly in force compared with control virgin animals. Although the resting membrane potentials were similar, the electric slow waves of pregnant animals displayed significant decreases in upstroke amplitude, plateau amplitude, and number of spikes during the plateau potential compared with control animals. The voltage-tension relationship was similar in pregnant and control animals.

CONCLUSIONS

This study indicates that (1) the force of antral circular muscle contractions is decreased during pregnancy and (2) this decreased force is secondary to a diminished slow wave depolarization. The results suggest that a change in electromechanical activity of gastric muscle is a cause of altered gastric motility in pregnancy.