Evidence for decidual modulation of contractile function in the pregnant rat uterus

This study tested the hypothesis that the decidua of pregnant uterus modulates contractile behavior of the underlying myometrium. Isometric contractile function was measured in transverse rings of pregnant rat uterus with or without the decidua. Observations were made of spontaneous contractions after in vitro isolation, and also of contractile responses to oxytocin and prostaglandin F2 alpha (PGF2 alpha) after the tissues had ceased spontaneous mechanical activity. The amplitude and frequency of spontaneous uterine contractions progressively declined after in vitro isolation; during this period, amplitude of spontaneous contractions was greater in the presence of the decidua, whereas contraction frequency was similar in the decidua-intact and decidua-removed tissues. Reinsertion of donor decidua reproduced contractile characteristics of intact tissue. PGF2 alpha and oxytocin stimulated myometrial contractions, but contraction frequency was greater in the absence than in the presence of the decidua. Depending upon the stimulus, the decidua seems able to express both excitatory and inhibitory factors which can selectively modulate either strength or frequency of uterine contractions.