(O-10) Local Effect of Allopregnanolone in Rat Ovarian Steroidogenesis, Follicular and Corpora Lutea Development

Abstract Authors: Antonella Rosario Ramona Cáceres^1,2; Daniela Alejandra Cardone¹; María de los Ángeles Sanhueza¹; Myriam Raquel Laconi^1,2.

¹Laboratorio de Fisiopatología Ovárica, Instituto de Medicina y Biología Experimental de Cuyo (IMBECU – CONICET Mendoza), Mendoza, Argentina.

²Facultad de Ingeniería y Facultad de Ciencias Médicas, Universidad de Mendoza, Mendoza, Argentina.

Abstract Text: Allopregnanolone (ALLO) is a known neurosteroid and a progesterone metabolite synthesized in the ovary, central nervous system, peripheral nervous system, adrenals and placenta. Its role in the neuroendocrine control of ovarian physiology has been studied, but its in situ ovarian effects are still largely unknown. The aims of this work were to characterize the effects of ALLO intrabursal administration on different ovarian parameters, and the probable mechanism of action. ALLO administration increased serum progesterone concentration (p=0.0010, n=5) and ovarian 3β-HSD (p=0.0451, n=4) while decreasing 20α-HSD mRNA expression (p=0.0137, n=4). ALLO increased the number of atretic follicles (p=0.0077, n=4), and the number of positive TUNEL granulosa and theca cells (theca: p=0.0019 and granulosa: p< 0.0001, 16 sections/ovary, 5 ovaries/group), while decreasing positive PCNA immunostaining (theca: p=0.0312 and granulosa: p< 0.0003). Meanwhile, the diameter of corpora lutea (p< 0.0001, n=300 CL) and the PCNA immunostaining increased (p< 0.0001, 16 sections/ovary, 5 ovaries/group), while decreasing TUNEL positive cells (p< 0.0001, 16 sections/ovary, 5 ovaries/group). Ovarian angiogenesis (α-actin p=0.0005; Von Willebrand p=0.0058) and the GABA_A receptor immunohistochemical expression also increased after ALLO treatment. To evaluate if the ovarian GABA_A receptor was involved in these effects, we conducted a functional experiment with a specific antagonist, bicuculline. The administration of bicuculline returned the number of atretic follicles (p=0.0002, n=5 animals/group) and the diameter of corpora lutea (p< 0.0001, n=5 animals/group, 51 CL/group) to normal values. These results show ALLO actions on the ovarian physiology of the female rat during the follicular phase, some of them through the GABA_AR. Intrabursal ALLO administration alters several processes of the ovarian morpho-physiology of the female rat, related to fertility and oocyte quality.