Comparison between prostaglandin E2 and oxytocin actions on pregnant mouse myometrium.

Effects of prostaglandin E2 (PGE2) and oxytocin on the membrane activity of pregnant mouse myometrium were investigated with the microelectrode method. Sensitivity of the myometrium to oxytocin increased only during the last stage of gestation, however sensitivity to PGE2 gradually increased beginning at the middle stage of gestation. Prolonged treatment with PGE2 but not with oxytocin produced desensitization of the myometrium. When the membrane potential was electrically displaced to the resting level after the membrane had been markedly depolarized by either PGE2 or oxytocin, spike activity was restored. However with PGE2 there was continuous spike generation and with oxytocin periodic burst discharges with silent periods. In Ca-free Locke solution, PGE2 and oxytocin still produced depolarization of the membrane, however, oxytocin produced larger depolarization. The different responses of the membrane to PGE2 and oxytocin are discussed in relation to the roles of Ca ion and to the ovarian and placental hormones during gestation.