Intraperitoneal injection of either melatonin or indomethacin on days 19 and 20 of pregnancy in mice led to a delay in the onset and signific ant prolongation in the duration of spontaneous labour. The incidence of foetal mortality was low and a non-significant change in the mean number of alive pups was obtained.
in animais treated with melatonin on days 15, 16 and 17 of pregnancy after prostaglandin FPGF, ), the day of labour was 20. 88+0.23 and the mean number of pups was 6.88+0.81 (all were born alive). Day of labour after PGF alone was 18.2 5+0.16 and mean number of pups was 6.5+063. A nearly similar effect to melatonin was obtained
in animals treated with indomethacin.
Histological examination of the embryos of mice treated with melatonin on days ), 10 and 11 of pregnancy after PGF, a showed many number of mitosis indicating inhibition of the abortive effect of prostaglandin. Sections of embryos of animals treated with indomethacin showed nearly similar picture to that of melatonin.
In vitro study: melatonin produced significant decrease in the amplitude and frequency of uterine contraction. Both melatonin and indomethacin antagonised the stimulatory effect of PGF, a on uterine contractions.
From this study, it can be concluded that melatonin has some similar effects to that of indomethacin on prostaglandins.