Figure 1. Melatonin enhances the blastocyst formation rate of prolonged-culture oocytes. Porcine oocytes matured in vitro were continuously cultured in medium supplemented with or without melatonin (10−3 or 10−5 M) for 24 h. Oocytes were pathogenetically activated and then cultured for 7 days to examine the blastocyst formation rate. Views of blastocysts (A) and blastocyst formation rate (B) of fresh, prolonged-culture, and prolonged-culture + Mel oocytes. The data are presented as the mean ± SEM of at least three independent experiments. Bar=200 μm; PC, prolonged-culture; Mel, melatonin; *P<0.05, **P<0.01.