Action of prostaglandin, PGF2alpha, on the uterus of the pregnant rat.

The effects of prostaglandin F2alpha (PG) have been studied on the transmembrane potentials and contractions in isolated myometrial strips from pregnant rats. The results showed that: 1. The sensitivity of the myometrium to exogenous PG increases from day 19 to day 22 of gestation. 2. The electrical response to PG, at maximally effective doses (10-6 to 10-5 M) consists of a slow depolarization which upon reaching threshold initiates spike discharge. 3. These actions are most pronounced at term (day 22) and are due to a direction of PG on the myometrial cells. 4. D-600 (a methoxy derivative of verapamil) abolishes spike discharge and the phasic contractions induced by PG but has no effect on the slow depolarization and the accompanying increase in tonic tension. 5. The slow depolarization is dependent upon the presence of sodium in the external environment and is unaffected by the removal of calcium. 6. The spikes (and phasic contractions) are dependent upon the presence of calcium in the external environment.