Effects of prostaglandin F2α, oxytocin, and ethanol on the uterus of the pregnant baboon

Abstract

The effects of oxytocin and prostaglandin F2α (PGF2α) on uterine contractions in the pregnant baboon were examined at term. Oxytocin at a threshold dose of 4 mU. per minute and above induced an increase of both frequency and amplitude of contractions without significant evidence of hypertonicity. The stimulatory effect of PGF2α at the threshold of 20 μg per minute and higher had a rapid onset, with contractions of high frequency but low amplitude accompanied by occasional transient elevated uterine tonus; subsequently the tonus waned and contractions became rhythmic and regular. Similar findings have been reported in human beings. PGF2α had a marked sustained stimulatory effect on the uterus. One hour after the discontinuance of PGF2α the uterine activity had decreased by only 18 per cent, whereas the uterine activity at the same time after discontinuation of the oxytocin infusion had decreased by 50 per cent. Ethanol did not inhibit PGF2α-induced uterine activity whether administered prior to or during PGF2α infusion of 20 μg per minute or higher. The response to oxytocin at the threshold level of 4 mU. per minute was diminished by ethanol but ethanol did not diminish uterine response to the higher doses of 8 and 15 mU. of oxytocin per minute.