The trigger for parturition in sheep: fetal hypothalamus or placenta?

摘要: The fetal pituitary-adrenal axis plays a pivotal role in the mechanisms leading to parturition sheep. Fetal cortisol concentrations gradually increase last 15 days before term, with marked occurring 3-4 days. Some mechanism causes stimulatory drive pituitary resulting increased secretion of ACTH from pituitary, and subsequent adrenal gland. In this paper we discuss roles hypothalamus placenta triggering onset labour We have shown that prostaglandin E2 can stimulate release intact fetus believe could be mediated by CRH AVP. Although AVP are present capable being released, these factors may not released until approximately 135 gestation. One fundamental question relation remains unanswered: how high plasma sustained given has an inhibitory feedback effect on secretion? possibility provides additional trophic both glands which contributes towards elevated needed initiate parturition. PGE2 and/or CRH, secreted placenta, release.