Exogenous progesterone or indomethacin delays parturition in the viviparous lizard Sceloporus jarrovi

Female Sceloporus jarrovi in late pregnancy given an ip injection of progesterone (50 ng/g body wt) or indomethacin (4 μg/g body wt) exhibited no change in the length of pregnancy when compared to saline-treated controls. In contrast, pregnant females given subcutaneus implants (constant release pellets) containing progesterone or indomethacin exhibited significantly delayed parturition when compared with females given control implants. Indomethacin treatment also disrupted the normal birth process when it occurred, as all females recieving this compound exhibited parturition of only a portion (24–32%) of the total clutch. A similar phenomenon occurred in one experiment following implantation of progesterone pellets. Histological examination of the corpora lutea and oviduct indicated no obvious difference in structure among any of the treatment groups.