Effect of Prostaglandin F2α Administration on Contractility of the Female Reproductive Tract of the Rabbit

Abstract

Effects of prostaglandin F_2α (PGF_2α) on the contractile activity of the oviductal isthmus, uterus and cervix in rabbits before and after mating were investigated by recording changes of their intraluminal pressures. PGF_2α(2 or 5mg/kg of body weight) was subcutaneously administered to rabbits prior to mating and then at 24 or 48 hours after mating. Effects of readministration of PGF_2α 1 or 2 hours later were also studied in estrous rabbits. PGF_2α effected an increase in the muscular activity of all organs examined. The responsive pattern was characterized by a spasmodic contraction, and in the uterus and cervix there was another pattern showing an increase in the amplitude and frequency but no change in tone. Readministration of 2mg/kg of PGF_2α 1 hour later caused a strong contraction as occurred earlier only in the uterus, while the second PGF_2α injected 2 hours later brought about stimulatory effects on the motility of each organ similar to those after the first PGF_2α injection. Readministration of 5mg/kg of PGF_2α 1 or 2 hours later evoked little or a slight stimulatory effect of the contractions of each organ, respectively. Administration of PGF_2α 24 hours after mating caused strong contractions in each organ, similarly at estrus. The effectiveness of PGF_2α in stimulating the motility of each organ was less remarkable when injected 48 hours after mating. It was concluded that the effectiveness of multiple injections of PGF_2α varies with dose and interval, and that the sensitivity of the reproductive organs to this drug decreases by at least 48 hours after mating.