The key action of estradiol and progesterone enables GnRH delivery during gestation in the South American plains vizcacha, Lagostomus maximus

Abstract

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Hypothalamic GnRH expression and pulsatility depends on a balance of prolactin receptors in the plains vizcacha, Lagostomus maximus

“…Immediately after brains removal, whole hypothalami were dissected out to a depth of approximately 4 mm up to the subthalamic sulcus and following the anterior and lateral borders of the optic chiasm (oc) and the anterior border of the mammillary bodies, as previously described in Dorfman et al (2013) and Inserra et al (2017Inserra et al ( , 2020.…”

“…GnRH and LH pulsatilities were measured ex vivo as previously described in mice (Catalano et al, 2010) and vizcacha (Charif et al, 2016;Inserra et al, 2020;Proietto et al, 2019). Briefly, dissected hypothalami and anterior pituitaries explants of control (CTL, n = 4)…”

“…GnRH and LH released by hypothalamic or pituitary explants respectively, were measured by RIA as previously described in mice (Di Mongiat et al, 2006) and in vizcacha (Charif et al, 2016;Dorfman et al, 2013;Inserra et al, 2020;Proietto et al, 2019).…”

“…GnRH and LH concentrations were analyzed in duplicate. GnRH was measured by specific RIA using anti-GnRH antiserum (rabbit polyclonal HU-60 that recognizes GnRH1 with higher affinity than GnRH2, final dilution 1:50,000) kindly provided by Dr. Urbanski (Division of Neuroscience, Oregon National Primate Research Center) as previously described (Dorfman et al, 2013;Inserra et al, 2020).…”

Achieving full-term pregnancy in the vizcacha relies on a reboot of luteal steroidogenesis in mid-gestation (Lagostomus maximus, Rodentia)

“…In addition, early in pregnancy, the onset of placental calcification and thinning of the uterine segmental arteries as they move away from the cervix and toward the ovary strongly suggest that the vizcacha placenta is, at best, steroidogenically deficient [22][23][24]. As a result of the decrease in circulating progesterone represented in the "valley" of the biphasic curve around day 90 of gestation, and the consequent elimination of negative feedback on gonadotropin release, a new set of accessory CL (aCL) arises in the midgestation [21,[25][26][27]. It has been attributed precisely to these aCL the recovery of the progesterone levels necessary to adequately complete embryonic development and to carry the pregnancy to term [21].…”