Ruolo dei peptidi oppioidi endogeni (EOP) come coregolatori ad azione locale della maturazione dell'ovocita e dell'embriogenesi in vitro negli equini

Summary In this study, we report the detection of the mu-opioid receptor in equine cumulus-oocyte complexes, both at the mRNA and the protein end product level. The effects of beta-endorphin and of the opioid antagonist naloxone (Nx) on the maturation rate (MR) and cytoskeletal organization (microtubules and microfila- ments) of oocytes recovered in different seasons of the year (spring transition, breeding season, autumnal transition and winter anestrous) and showing initial compact or expanded cumulus oophorus morphology have been examined by confocal laser scanning microscopy (CLSM). In parallel, modifications of intra- cellular calcium concentration ([ C a^ 2+ ] i ) in cumulus cells incubated in presence of Nx or beta-endorphin have been evaluated by microspectofluorimetry. Variable effects of Nx and beta-endorphin on MR, cytoskeletal organization and [ C a^ 2+ ] may be related to different levels of mu-opioid receptor expression or activation status that could underlay different meiotic competence of equine oocytes.