ACTION OF ADRENALINE AND POTENTIAL CHANGES IN THE CAT UTERUS

¹ From the Nuffield Institute for Medical Research, Oxford, England

1. In the anestrous cat uterus spontaneous slow rhythmic potential changes occur. They continue, and are slightly increased, during a relaxation produced by adrenaline, but they are abolished or greatly diminished during a relaxation produced by ephedrine. Very similar phenomena occur in the intestine.

2. Eserine has no effect on the action of adrenaline in the anestrous cat uterus.

3. In estrus and in late pregnancy uterine contractions, whether occurring spontaneously or by the action of a drug, are accompanied at the beginning of the contraction by short bursts of spike potentials, with a frequency of 1 to 3 per second and an individual duration of 0.2 to 0.4 second.

4. In early pregnancy and during progestational proliferation, spike potentials accompanying spontaneous contractions are greatly diminished in number and magnitude and are often abolished. In this state the mechanical reaction to adrenaline is reversed. Uterine contractions produced by drugs are accompanied by more spike potentials than are spontaneous contractions, but much fewer than arise from contractions of the estrous uterus.

5. It is suggested that the conduction of impulses from cell to cell is a characteristic of estrous uteri (in all species so far examined), and is responsible for the strong and coordinated contractions which occur during this period. In anestrous uteri such conduction does not occur, and during progestational proliferation it is partially suppressed; the uterine contractions are correspondingly feeble during these phases. Conduction may or may not occur during pregnancy, depending on whether the estrogenic or luteal hormone predominates.

6. The reversal of the mechanical response of the cat uterus to adrenaline during pregnancy and progestational proliferation is discussed, and a possible mechanism outlined.