Hypothalamic-hypophyseal-gonadal axis activity in the south american plains vizcacha during gestation.

INSERRA PIF; CHARIF S; REY-FUNES M; SAUCEDO L; DI GIORGIO NP; LUX-LANTOS V; VITULLO AD; DORFMAN, VB

Logroño

Congreso; XVII Congreso de la Sociedad Española de Histología e Ingeniería Tisular; 2013

Sociedad Española de Histología e Ingeniería Tisular

The correct operation of the hypothalamic-hypophyseal-gonadal (HHG) axis is essential to ensure fertility and reproductive efficiency. The gonadotropin releasing hormone (GnRH) is the key regulator of the HHG axis. GnRH pulsatility activates hypophyseal function resulting in delivery of the gonadotropins, follicular stimulating hormone (FSH) and lutheal hormone (LH). Both hormones stimulate ovarian folliculogenesis and luteolysis with increments on estradiol (E2) and progesterone (Pg) secretion. Then, both steroid hormones act over the hypothalamus modulating GnRH synthesis and delivery. Estrogen Receptors a and b (ERa and ERb) are able to induce GnRH expression acting as transcription factors directly on GnRH promoter specif sites or non-directly stimulating the transcription of progesterone receptors (PR) which can in turn induce GnRH expression. In most mammals, this cycle repeats from puberty to menopause except in pregnancy. Previous studies showed that the South American plains vizcacha (Lagostomus maximus) ovulate up to 800 oocytes per reproductive cycle, and show folliculogenesis progressing to pre-ovulatory stages with a possible ovulatory event at mid-gestation. The aim of this work was to analyze hypothalamic ERa, ERb, and PR expression through gestation in the vizcacha, to relate it with GnRH and LH secretion, and with the functional state of the ovary in gestating females. We used plains vizcachas at early- and mid-pregnancy to investigate hypothalamic GnRH and serum LH, E2 and Pg levels, and GnRH, ERa, ERb and PR hypothalamic localization and expression, by ELISA, RIA, Immunohistochemistry, Immunofluorescence and Western-blot. Hypothalamic immunolocalization of ERa, ERb and PR was observed in neurons of preoptic area (PA), supraoptic nucleus (SON) and median eminence (ME), with similar distribution among groups, whereas, GnRH was localized in somas and axonic varicosities at the same regions. In addition, ERa, ERb and PR were co-localized in the same neurons, while only a few neurons of preoptic area showed co-expression of PR and GnRH. The analysis of ERa, ERb and PR expression throughout pregnancy showed that ERa and PR significantly varied during gestation (p