Effect of continuous infusion of oxytocin on ovarian function and uterine oxytocin receptor concentration in the cyclic ewe [sheep]
1992
Sheldrick, E.L. (AFRC Inst. of Animal Physiology and Genetics Research, Babraham (United Kingdom))
To investigate whether inhibition of oxytocin receptor binding activity by oxytocin is either dependent on elevated plasma progesterone concentrations or over-ridden by oestrogens secreted by ovarian follicles maturing as a result of cloprostenol treatment, ewes were given oxytocin by continuous intravenous infusion. Treatment with oxytocin alone resulted in the maintenance of corpora lutea, reduced follicular development and a low concentration of uterine oxytocin receptor. Cloprosenol initiated luteolysis in oxytocin-treated ewes. This was associated with a high level of oxytocin receptor binding activity in all ewes except those receiving exogenous progesterone. The data showed that, although down-regulation of the oxytocin receptor by oxytocin is progesterone-dependent, administration of a pharmacological dose of oestradiol-17beta stimulates receptor synthesis in the presence of high concentrations of both progesterone and oxytocin, but it does not cause luteolysis.
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