EFFECT OF STRESS ON THE COURSE OF LABOR AND PARTURITION TIME IN NORMAL OR ADRENALECTOMIZED RATS

We report two experiments studying the effect of stress on the course of labor and on the time of parturition in the parturient rat. In the first experiment, different stresses were applied after expulsion of the first fetus. A simple manipulation of the female or a change of territory did not modify the whole expulsion phase but increased variability in the birth of the second fetus. By comparison, a strong stress lengthened the duration of expulsion and influenced the time intervals between the first births. A comparison of these results with those obtained after adrenalectomy indicated that the inhibitory effect of a strong stress was probably due to maternal adrenal epinephrin secretion. In the second experiment, a stress was applied before labor in normal rats submitted to two light regimes. In these conditions, the treatment essentially stimulated the last parturitions, which occurred earlier than in control animals.