Naloxone increases maturation rate and ratio of innercell mass to total cells in blastocysts in pigs

摘要

The purposes of the present study were to examine the effect of naloxone, a mu-opioid receptor (MOR) antagonist, onporcine oocyte maturation and embryo development. MOR gene was expressed in germinal vesicle (GV) and metaphaseII (M-II) porcine oocytes, one-, four-cell stage embryos and blastocysts. In blastocysts, MOR gene was mainly expressed ininner cell mass (ICM) cells. Supplementation of 10-8 mol/L naloxone in in vitro maturation (IVM) medium increased thematuration rate (P < 0.05). However, 10-4 mol/L naloxone reduced the maturation rate (P < 0.05) compared with thecontrol. The presence of naloxone during IVM had no effects on fertilization status and subsequent embryonic developmentafter in vitro culture (IVC). The addition of 10-3 mol/L dibutyryl cyclic adenosine monophosphate (dbcAMP), and10-8 mol/L naloxone together into IVM medium increased nuclear maturation (P < 0.05) compared with the addition ofeither dbcAMP or naloxone alone. Supplementation with naloxone in IVC medium did not improve embryonic development.However, at the concentrations of 10-6 mol/L and 10-8 mol/L, naloxone increased the ratio of ICM to total cells inblastocysts (P < 0.05). In conclusion, at low concentration, naloxone increases maturation rate and the ratio of ICM to totalcells in blastocysts. Naloxone and cAMP have a synergistic effect on oocyte maturation.