ACTION OF OUABAIN ON THE GUINEA-PIG ISOLATED UTERUS.

Uterine activity in vitro was measured isometrically by integrating tension against time, and contractions were recorded on a kymograph using a servo-recorder. Ouabain caused a persistent contraction both of the spontaneously contracting and of the electrically stimulated uterus, the response depending upon the presence of calcium. After ouabain had induced a contraction of the spontaneously active uterus, relaxation to the baseline after washing out the ouabain was succeeded by a period of inactivity. Since the uterus could respond as usual to stimulation during this period, ouabain appeared to be selectively depressing spontaneous contractions. High concentrations of progesterone suppressed uterine activity and the response to ouabain. Ouabain reduced the susceptibility of the uterus to depression by anoxia.