Variation in Progesterone Receptors and GnRH Expression in the Hypothalamus of the Pregnant South American Plains Vizcacha, Lagostomus maximus (Mammalia, Rodentia)

VERONICA BERTA DORFMAN; LUCIA SAUCEDO ; NOELIA PAULA DI GIORGIO; PABLO I INSERRA; NICOLAS FRAUNHOFFER; NOELIA P LEOPARDO; JULIA HALPERIN; VICTORIA LUX-LANTOS; ALFREDO DANIEL VITULLO

BIOLOGY OF REPRODUCTION

SOC STUDY REPRODUCTION

Lugar: Madison; Año: 2013 vol. 89 p. 1 - 12

0006-3363

In mammals, elevated levels of progesterone (P4) throughout gestation maintain a negative feedback over the hypothalamic-hypophyseal-gonadal (H-H-G) axis avoiding pre-ovulatory follicular growth and preventing ovulation. Recent studies showed that in the South American plains vizcacha (Lagostomus maximus) folliculogenesis progresses to pre-ovulatory stages during gestation, and an ovulatory process seems to occur at mid-gestation. The aim of this work was to analyze hypothalamic gonadotropin-releasing hormone (GnRH) and P4 receptors (PR) expression and luteinizing hormone (LH) secretion, and correlate these with the functional state of the ovary in non-ovulating and ovulating females, and gestating females with special emphasis in the supposedly ovulating females at mid-gestation. We investigated P4 and LH serum levels as well as the distribution, localization and expression of PR and GnRH in the hypothalamus of L. maximus at different time-points during gestation and in non-gestating, ovulating and non-ovulating, females. A significant increment in GnRH, P4 and LH was detected in mid-pregnant vizcachas with respect to early-pregnant and to ovulating females. PR was also significantly increased in mid-pregnant animals. PR was detected in neurons of the Preoptic and Hypothalamic areas. Co-existence of both PR and GnRH in neurons of medial preoptic area and supraoptic nucleus was detected. Mid-pregnant animals showed increased number of PR immunoreactive cells at median eminence, localized adjacently to GnRH immunoreactive fibers. High expression of hypothalamic GnRH and PR, despite an increased level of P4, was correlated with the presence of antral, pre-ovulatory follicles and luteinized unruptured follicles at mid-gestation that suggest a possible role of the H-H-G axis in the modulation of ovulation during gestation in L. maximus