Local production of neurostradiol affects gonadotropin-releasing hormone (GnRH) secretion at mid-gestation in Lagostomus maximus (Rodentia, Caviomorpha).

CHARIF, SE; INSERRA, PIF; SCHMIDT, AR; DI GIORGIO, NP; CORTASA, SA; GONZALEZ, CR; LUX-LANTOS, V; HALPERIN, J; VITULLO, AD; DORFMAN, VB

Physiological Reports

Wiley Periodicals Inc.

Año: 2017 vol. 5

Females of the South American plains vizcacha, Lagostomus maximus, showpeculiar reproductive features such as massive polyovulation up to 800oocytes per estrous cycle and an ovulatory process around mid-gestation arisingfrom the reactivation of the hypothalamic?hypophyseal?ovary (H.H.O.)axis. Estradiol (E2) regulates gonadotropin-releasing hormone (GnRH) expression.Biosynthesis of estrogens results from the aromatization of androgens byaromatase, which mainly occurs in the gonads, but has also been described inthe hypothalamus. The recently described correlation between GnRH and ERaexpression patterns in the hypothalamus of the vizcacha during pregnancy,with coexpression in the same neurons of the medial preoptic area, suggeststhat hypothalamic synthesis of E2 may affect GnRH neurons and contributewith systemic E2 to modulate GnRH delivery during the gestation. To elucidatethis hypothesis, hypothalamic expression and the action of aromatase onGnRH release were evaluated in female vizcachas throughout pregnancy. Aromataseand GnRH expression was increased significantly in mid-pregnant andterm-pregnant vizcachas compared to early-pregnant and nonpregnantfemales. In addition, aromatase and GnRH were colocalized in neurons of themedial preoptic area of the hypothalamus throughout gestation. The blockageof the negative feedback of E2 induced by the inhibition of aromatase resultedin a significant increment of GnRH-secreted mass by hypothalamic explants.E2 produced in the same neurons as GnRH may drive intracellular E2 tohigher levels than those obtained from systemic circulation alone. This maytrigger for a prompt GnRH availability enabling H.H.O. activity at mid-gestationwith ovulation and formation of accessory corpora lutea with steroidogenicactivity that produce the necessary progesterone to maintain gestationto term and guarantee the reproductive success.