Electrical and Mechanical Interaction between the Muscle Layers of Rat Uterus and Different Sensitivities to Oxytocin

The present experiment was carried out to investigate the interaction between the electrical and mechanical activities of longitudinal and circular muscle layers of the pregnant rat uterus. The following results were obtained. 1. The electrical activity of longitudinal and circular muscle layers was appeared in a burst which was corresponded with contraction. The features on th mechanical activity of those two layers were very different. Full-size contractions in the longitudinal layer and phasic contractions with various magnitudes in the circular one were obtained. 2. Spontaneous excitation was well conducted through the longitudinal muscle layer but such well propagation was not seen in the circular one usually. No synchronization between bursts from longitudinal and circular muscle layers was detected in the circular strip. However, the burst interaction between the layers was recorded in the L-shaped strip. The synchronization between the burst activities in the circular muscle layer was also observed in the L-shaped strip. 3. The sensitivities of longitudinal and circular muscles to oxyocin were different. Circular muscle was more insensitive to oxytocin. 4. It is concluded from the present experiment that the layers are coupled together and the excitation of one muscle layer is likely propagated into the other muscle layer by some interactions.