Evaluation of beta-endorphin and naloxone on bovine uterine motility

Abstract Effects of β-endorphin and naloxone on bovine uterine motility were tested both in vivo and in vitro. Six cyclic Holstein cows were used to study in vivo effects of β-endorphin and naloxone on uterine motility during estrus and diestrus. Intrauterine pressure changes were recorded by a microtip pressure transducer before and after treatment. Blood samples were taken every 10 min during the recording periods for β-endorphin assay. The results revealed that β-endorphin anc naloxone had no effect on intrauterine pressure in vivo. The effects of β-endorphin and naloxone on myometrial contractility were also examined in vitro. Beta-endorphin and naloxone were added to tissue baths containing estrous and diestrous uterine strips. The results showed no significant effect of β-endorphin and naloxone on bovine myometrial contractility. The role of β-endorphin in bovine reproductive physiology is still not clearly understood, and additional studies are needed.