REGULATION OF GnRH BY PROLACTIN IS ASSOCIATED TO CORPORA LUTEA ACTIVITY DURING PREGNANCY IN THE SOUTH AMERICAN PLAINS VIZCACHA,Lagostomus maximus

DORFMAN VB. CORTASA SA, SCHMIDT AR, PROIETTO S, CORSO MC, INSERRA PIF, DI GIORGIO NP, VITULLO AD; HALPERIN J

Concon

Congreso; XXIX Annual Meeting Sociedad Chilena de Reproducción y Desarrollo. septiembre 2018, Concón, Chile; 2018

Sociedad Chilena de Reproduccion y Desarrollo

Prolactin (PRL) promotes luteal steroidogenesis in rodents and inhibitshypothalamic?hypophyseal?ovaric axis during pregnancy. The South American plainsvizcacha shows GnRH increase at mid-pregnancy with ovulation and corpora lutea (CL)formation. Herein, we investigated PRL modulation of GnRH expression and deliveryand its relation to the CL development during gestation. We designed 2 experiments:1) study of total release of GnRH from hypothalamic explants (eHT) of non-pregnantvizcachas cultured for 6hs in media supplemented with either hyperprolactinemic orcontrol serum (n=5), 2) analysis of GnRH pulsatility in eHT of females treated for 7days with Sulpiride (20mg/Kg, n=5) or with saline solution (controls). In addition,hypothalamic immunoexpression of GnRH, dopamine receptor (DR2), tyrosinhydroxylase (TH) and PRL receptor (PRLR) was studied in early-, mid- and term-gestating vizcachas (n=5/group). The mass of GnRH released from eHT incubated for6hs with hyperprolactinemic serum was significantly increased related to controls(p<0.05). However, GnRH pulsatility was lower in hyperprolactinemic eHT compared tocontrols (p<0.05). The expression of GnRH, TH, DR2 and PRLR was studied in thehypothalamus of pregnant vizcachas to associate it with the dual effect of PRL onGnRH. TH-immunoreactive neurons were localized in the neighboring of GnRH-cells,whereas co-localization of GnRH with DR2, and of TH with PRLR, progressivelyincreased during pregnancy. These results suggest that the increase of GnRH at mid-gestation is induced by the concomitant increase of PRL which is also involved in CLformation, whereas the sustained exposition to PRL up to the term-gestation inhibitsGnRH pulsatility.