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9 February 2018 New insights on a NGF-mediated pathway to induce ovulation in rabbits (Oryctolagus cuniculus)
Margherita Maranesi, Linda Petrucci, Leonardo Leonardi, Federica Piro, Pilar García Rebollar, Pilar Millán, Paolo Cocci, Cecilia Vullo, Francesco Parillo, Arlindo Moura, Gabriela Gonzalez Mariscal, Cristiano Boiti, Massimo Zerani
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Abstract

To investigate the ovulatory mechanisms triggered by raw semen (RS) in rabbits, we examined the expression of nerve growth factor (NGF)—a supposed ovulation-inducing factor (OIF)—and cognate receptors in anterior pituitary, ovary, and cervix as well as plasma NGF and luteinizing hormone (LH) concentrations. Six does/group were sham-inseminated with sterile saline (PBS), naturally mated (NM), inseminated with RS alone or after lumbar anesthesia (ARS), or treatment with COX inhibitors (CIRS). Immunohistochemistry revealed positive signals for NGF and receptors in all tissues. RT-PCR confirmed the presence of the target transcripts in the same tissues, except NTRK1 in the cervix. Circulating NGF concentrations rose 3- to 6-fold (P < 0.01) 15 min after semen deposition into the genital tract of NM, RS, and ARS rabbits and remained sustained thereafter. Circulating NGF was 4-fold lower (P < 0.01) in CIRS than in RS does indicating that NGF is mainly synthesized by the uterus. A concomitant rise of LH and NGF concentrations was found in 83.3%, 50.0%, and 16.7% of NM, RS, and CIRS does, respectively, but not in ARS (despite high NGF circulating levels). Seminal plasma NGF concentration was 151.9 ± 9.25 µg/mL. The ovulatory responses were 0%, 83.3%, 66.7%, 16.7%, and 0% in PBS, NM, RS, ARS, and CIRS groups, respectively. Present data confirm that, although RS may induce ovulation via endocrine mechanisms through binding to NGF receptors in the ovary, a novel OIF-mediated neural mechanism facilitates ovulation in rabbits.

Summary Sentence

Raw semen induces ovulation in rabbits via an endocrine- and a nervous-mediated pathway by which NGF, mainly synthesized in the uterus, acts on the ovary and on uterine/cervix afferent neurons projecting LH surge hypothalamic centers, respectively.

© The Author(s) 2018. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com
Margherita Maranesi, Linda Petrucci, Leonardo Leonardi, Federica Piro, Pilar García Rebollar, Pilar Millán, Paolo Cocci, Cecilia Vullo, Francesco Parillo, Arlindo Moura, Gabriela Gonzalez Mariscal, Cristiano Boiti, and Massimo Zerani "New insights on a NGF-mediated pathway to induce ovulation in rabbits (Oryctolagus cuniculus)," Biology of Reproduction 98(5), 634-643, (9 February 2018). https://doi.org/10.1093/biolre/ioy041
Received: 28 July 2017; Accepted: 7 February 2018; Published: 9 February 2018
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