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Vertebrate reproductive science and technology
RESEARCH ARTICLE

Effects of intracerebroventricular infusions of ghrelin on secretion of follicle-stimulating hormone in peripubertal female sheep

Anna Wójcik-Gładysz A B , Marta Wańkowska A , Alina Gajewska A , Tomasz Misztal A , Marlena Zielińska-Górska A , Michał Szlis A and Jolanta Polkowska A
+ Author Affiliations
- Author Affiliations

A Polish Academy of Sciences, The Kielanowski Institute of Animal Physiology and Nutrition, 3 Instytucka st, 05-110 Jabłonna, Poland.

B Corresponding author. Email: a.wojcik@ifzz.pl

Reproduction, Fertility and Development 28(12) 2065-2074 https://doi.org/10.1071/RD16028
Submitted: 15 January 2016  Accepted: 23 April 2016   Published: 16 June 2016

Abstract

Reproduction depends on mechanisms responsible for the regulation of energy homeostasis and puberty is a developmental period when reproductive and somatic maturity are achieved. Ghrelin affects the activity of the hypothalamo–pituitary–gonadal axis under conditions of energy insufficiency. An in vivo model based on intracerebroventricular (i.c.v.) infusions was used to determine whether centrally administered acyl ghrelin affects transcriptional and translational activity of FSH in peripubertal lambs and whether ghrelin administration mimics the effects of short-term fasting. Standard-fed lambs received either Ringer–Lock (R-L) solution (120 µL h–1) or ghrelin (120 µL h–1, 100 µg day–1). Animals experiencing a short-term (72 h) fast were treated only with R-L solution. In each experimental group, i.c.v. infusions occurred for 3 consecutive days. Immunohistochemistry, in situ hybridisation and real-time reverse transcription quantitative polymerase chain reaction analyses revealed that short-term fasting, as well as exogenous acyl ghrelin administration to standard-fed peripubertal lambs, augmented FSHβ mRNA expression and immunoreactive FSH accumulation. In addition to the effects of ghrelin on FSH synthesis in standard-fed animals, effects on gonadotrophin release were also observed. Acyl ghrelin increased the pulse amplitude for gonadotrophin release, which resulted in an elevation in mean serum FSH concentrations. In conclusion, the present data suggest that ghrelin participates in an endocrine network that modulates gonadotrophic activity in peripubertal female sheep.

Additional keywords: fasting, foliculotropin secretion, pituitary.


References

Ahmed, H. H., Khalil, W. K., Shousha, W. G., El-Sayed, E. S., Eskander, E. F., and Selim, R. E. (2012). Effect of food restriction on reproductive-related genes and reproductive hormones in adult female rats. Eur. Rev. Med. Pharmacol. Sci. 16, 1680–1690.
| 1:STN:280:DC%2BC3s7kt1Oktg%3D%3D&md5=b60b7d42a6a01139ee20f8078278246bCAS | 23161040PubMed |

Angelidis, G., Dafopoulos, K., Messini, C. I., Valotassiou, V., Georgoulias, P., and Messinis, I. E. (2012). Ghrelin: new insights into female reproductive system associated disorders and pregnancy. Reprod. Sci. 19, 903–910.
Ghrelin: new insights into female reproductive system associated disorders and pregnancy.Crossref | GoogleScholarGoogle Scholar | 22544849PubMed |

Beckett, J. L., Sakurai, H., Adams, B. M., and Adams, T. E. (1997). Moderate and severe nutrient restriction has divergent effects on gonadotroph function in orchidectomized sheep. Biol. Reprod. 57, 415–419.
Moderate and severe nutrient restriction has divergent effects on gonadotroph function in orchidectomized sheep.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2sXkslakt78%3D&md5=b14e1381ceb62b834a54e13c150f5bbeCAS | 9241058PubMed |

Castañeda, T. R., Tong, J., Datta, R., Culler, M., and Tschöp, M. H. (2010). Ghrelin in the regulation of body weight and metabolism. Front. Neuroendocrinol. 31, 44–60.
Ghrelin in the regulation of body weight and metabolism.Crossref | GoogleScholarGoogle Scholar | 19896496PubMed |

Chartrel, N., Alonzeau, J., Alexandre, D., Jeandel, L., Alvear-Perez, R., Leprince, J., Boutin, J., Vaudry, H., Anouar, Y., and Llorens-Cortes, C. (2011). The RF amide neuropeptide 26RFa and its role in the control of neuroendocrine functions. Front. Neuroendocrinol. 32, 387–397.
The RF amide neuropeptide 26RFa and its role in the control of neuroendocrine functions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXht1agu77F&md5=91a1c0cf900b88354461dd8e4308a1c1CAS | 21530572PubMed |

Cowley, M. A., Smith, R. G., Diano, S., Tschöp, M., Pronchuk, N., Grove, K. L., Strasburger, C. J., Bidlingmaier, M., Esterman, M., Heiman, M. L., Garcia-Segura, L. M., Nillni, E. A., Mendez, P., Low, M. J., Sotonyi, P., Friedman, J. M., Liu, H., Pinto, S., Colmers, W. F., Cone, R. D., and Horvath, T. L. (2003). The distribution and mechanism of action of ghrelin in the CNS demonstrates a novel hypothalamic circuit regulating energy homeostasis. Neuron 37, 649–661.
The distribution and mechanism of action of ghrelin in the CNS demonstrates a novel hypothalamic circuit regulating energy homeostasis.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXhvFelt7c%3D&md5=e746f0777eb542af82ae32cfe9d2b451CAS | 12597862PubMed |

Date, Y., Kojima, M., Hosoda, H., Sawaguchi, A., Mondal, M., Suganuma, T., Matsukura, S., Kangawa, K., and Nakazato, M. (2000). Ghrelin, a novel growth hormone-releasing acylated peptide, is synthesized in a distinct endocrine cell type in the gastrointestinal tracts of rats and humans. Endocrinology 141, 4255–4261.
| 1:CAS:528:DC%2BD3cXnslKgs7w%3D&md5=5f42e9a44c54a8f60d377cb3b7de368bCAS | 11089560PubMed |

Delhanty, P. J. D., Huisman, M., Julient, M., Mouchein, K., Brune, P., Themmen, A. P. N., Abribat, T., and van der Lely, A. J. (2015). The acylated (AG) to unacylated (UAG) ghrelin ratio in esterase inhibitor-treated blood is higher than previously described. Clin. Endocrinol. (Oxf.) 82, 142–146.
| 1:CAS:528:DC%2BC2cXitFOgs7bL&md5=1789794684c93f0e28aaa7991d7b3e86CAS |

Evans, J. J., and Anderson, G. M. (2012). Balancing ovulation and anovulation: integration of the reproductive and energy balance axes by neuropeptides. Hum. Reprod. Update 18, 313–332.
Balancing ovulation and anovulation: integration of the reproductive and energy balance axes by neuropeptides.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xmt1SnsL8%3D&md5=a6076d8eb19b1704fd621cf5d018b2fcCAS | 22442260PubMed |

Fernández-Fernández, R., Tena-Sempere, M., Aguilar, E., and Pinilla, L. (2004). Ghrelin effects on gonadotropin secretion in male and female rats. Neurosci. Lett. 362, 103–107.
Ghrelin effects on gonadotropin secretion in male and female rats.Crossref | GoogleScholarGoogle Scholar | 15193764PubMed |

Fernández-Fernández, R., Tena-Sempere, M., Navarro, V. M., Barreiro, M. L., Castellano, J. M., Aguilar, E., and Pinilla, L. (2005). Effects of ghrelin upon gonadotropin-releasing hormone and gonadotropin secretion in adult female rats: in vivo and in vitro studies. Neuroendocrinology 82, 245–255.
| 16721030PubMed |

Fernández-Fernández, R., Martini, A. C., Navarro, V. M., Castellano, J. M., Dieguez, C., Aguilar, E., Pinilla, L., and Tena-Sempere, M. (2006). Novel signals for the integration of energy balance and reproduction. Mol. Cell. Endocrinol. 254–255, 127–132.
Novel signals for the integration of energy balance and reproduction.Crossref | GoogleScholarGoogle Scholar | 16759792PubMed |

Fernández-Fernández, R., Tena-Sempere, M., Roa, J., Castellano, J. M., Navarro, V. M., Aguilar, E., and Pinilla, L. (2007). Direct stimulatory effect of ghrelin on pituitary release of LH through a nitric oxide-dependent mechanism that is modulated by estrogen. Reproduction 133, 1223–1232.
Direct stimulatory effect of ghrelin on pituitary release of LH through a nitric oxide-dependent mechanism that is modulated by estrogen.Crossref | GoogleScholarGoogle Scholar | 17636176PubMed |

Gahete, M. D., Rincón-Fernández, D., Villa-Osaba, A., Hormaechea-Agulla, D., Ibáñez-Costa, A., Martinez-Fuentes, A. J., Gracia-Navarro, F., Castaño, J. P., and Luque, R. M. (2014). Ghrelin gene products, receptors, and GOAT enzyme: biological and pathophysiological insight. J. Endocrinol. 220, R1–R24.
Ghrelin gene products, receptors, and GOAT enzyme: biological and pathophysiological insight.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXhtlGitLg%3D&md5=e9baa95201cd1b8ec7e24d6426643c1cCAS | 24194510PubMed |

Halvorson, L. M., Weiss, J., Bauer-Dantoin, A. C., and Jameson, J. L. (1994). Dynamic regulation of pituitary follistatin messenger ribonucleic acids during the estrous cycle. Endocrinology 134, 1247–1253.
| 1:CAS:528:DyaK2cXitVyrsbk%3D&md5=aae2481b2c241192bce9de3182cc7a46CAS | 8119165PubMed |

Harrison, J. L., Miller, D. W., Findlay, P. A., and Adam, C. L. (2008). Photoperiod influences the central effects of ghrelin on food intake GH and LH secretion in sheep. Neuroendocrinology 87, 182–192.
Photoperiod influences the central effects of ghrelin on food intake GH and LH secretion in sheep.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXkvVGrsrg%3D&md5=762393945a0c027321b668c274d8f6f3CAS | 18073457PubMed |

Holst, B., Cygankiewicz, A., Jensen, T. H., Ankersen, M., and Schwartz, T. W. (2003). High constitutive signaling of the ghrelin receptor-identification of a potent inverse agonist. Mol. Endocrinol. 17, 2201–2210.
High constitutive signaling of the ghrelin receptor-identification of a potent inverse agonist.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXoslKgtbc%3D&md5=5fe94a2c24046cbf52f3f99192187fb2CAS | 12907757PubMed |

Hosoda, H., Kojima, M., Mizushima, T., Shimizu, S., and Kangawa, K. (2003). Structural divergence of human ghrelin. Identification of multiple ghrelin-derived molecules produced by post-translational processing. J. Biol. Chem. 278, 64–70.
Structural divergence of human ghrelin. Identification of multiple ghrelin-derived molecules produced by post-translational processing.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38XpvVWns70%3D&md5=787d429fa9045a6f3a2c4eb911a79ccbCAS | 12414809PubMed |

Hurbain-Kosmath, I., Berault, A., Noel, N., Polkowska, J., Bohin, A., Leiter, M. J. E. H., Beamer, W. G., Bedigian, H. G., Davisson, M. T., and Harrison, D. E. (1990). Gonadotropes in a novel rat pituitary tumor cell line RC-4B/C. Establishment and partial characterisation of the cell line. In Vitro Cell. Dev. Biol. 26, 431–440.
Gonadotropes in a novel rat pituitary tumor cell line RC-4B/C. Establishment and partial characterisation of the cell line.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK3cXkvFWlsbw%3D&md5=76ac75b060d9760680817801e82a86f1CAS | 2161825PubMed |

Iqbal, J., Kurose, Y., Canny, B., and Clarke, I. J. (2006). Effects of central infusion of ghrelin on food intake and plasma levels of growth hormone, luteinizing hormone, prolactin, and cortisol secretion in sheep. Endocrinology 147, 510–519.
Effects of central infusion of ghrelin on food intake and plasma levels of growth hormone, luteinizing hormone, prolactin, and cortisol secretion in sheep.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XptFKn&md5=ec4300bb770ffcb26a75002c72f4e782CAS | 16210361PubMed |

Kageyama, H., Takenoya, F., Shiba, K., and Shioda, S. (2010). Neuronal circuits involving ghrelin in the hypothalamus-mediated regulation of feeding. Neuropeptides 44, 133–138.
Neuronal circuits involving ghrelin in the hypothalamus-mediated regulation of feeding.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXis1Sgsrg%3D&md5=4ea15cc8c39c03ccde888044c8630055CAS | 20036003PubMed |

Kile, J. P., Alexander, B. M., Moss, G. E., Hallford, D. M., and Nett, T. M. (1991). Gonadotropin-releasing hormone overrides the negative effect of reduced dietary energy on gonadotropin synthesis and secretion in ewes. Endocrinology 128, 843–849.
Gonadotropin-releasing hormone overrides the negative effect of reduced dietary energy on gonadotropin synthesis and secretion in ewes.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK3MXht1Slsro%3D&md5=781e38cc5ed8b09afcf0cdbdb3fa17f6CAS | 1899222PubMed |

Kirchner, H., Gutierrez, J. A., Solenberg, P. J., Pfluger, P. T., Czyzyk, T. A., Willency, J. A., Schurmann, A., Joost, H. G., Jandacek, R., Hale, J. E., Heiman, M. L., and Tschöp, M. H. (2009). GOAT links dietary lipids with the endocrine control of energy balance. Nat. Med. 15, 741–745.
GOAT links dietary lipids with the endocrine control of energy balance.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXmvVersrY%3D&md5=8666267df52c0061684b7ace24bc3bb6CAS | 19503064PubMed |

Kluge, M., Uhr, M., Bleninger, P., Yassouridis, A., and Steiger, A. (2009). Ghrelin suppresses secretion of follicle stimulating hormone (FSH) in males. Clin. Endocrinol. (Oxf.) 70, 920–923.
Ghrelin suppresses secretion of follicle stimulating hormone (FSH) in males.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXmvVCjtro%3D&md5=ec6c62766a551c9052a9ad81a2a63290CAS | 19054012PubMed |

Knox, K. L., Bauer-Dantoin, A. C., Levine, J. E., and Schwartz, N. B. (1995). Unmasking of neuropeptide-Y inhibitory effects on in vitro gonadotropin secretion from pituitaries of metestrous, but not proestrous rats. Endocrinology 136, 187–194.
| 1:CAS:528:DyaK2MXjt1Knt7Y%3D&md5=915f122a959bbedf3e0806a4831560deCAS | 7828530PubMed |

Kogawa, K., Nakamura, T., Sugino, K., Takio, K., Titani, K., and Sugino, H. (1991). Activin-binding protein is present in pituitary. Endocrinology 128, 1434–1440.
Activin-binding protein is present in pituitary.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK3MXhsFOgtLo%3D&md5=555cbdb557e29534f9a6e86a29daae22CAS | 1900230PubMed |

Kojima, M., Hosoda, H., Date, Y., Nakazato, M., Matsuo, H., and Kangawa, K. (1999). Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature 402, 656–660.
Ghrelin is a growth-hormone-releasing acylated peptide from stomach.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3cXjs1Ki&md5=4f45543a7e2bb8bab614a46f46cddf84CAS | 10604470PubMed |

Lanfranco, F., Bonelli, L., Baldi, M., Me, E., Broglio, F., and Ghigo, E. (2008). Acylated ghrelin inhibits spontaneous luteinizing hormone pulsatility and responsiveness to naloxone but not that to gonadotropin-releasing hormone in young men: evidence for a central inhibitory action of ghrelin on the gonadal axis. J. Clin. Endocrinol. Metab. 93, 3633–3639.
Acylated ghrelin inhibits spontaneous luteinizing hormone pulsatility and responsiveness to naloxone but not that to gonadotropin-releasing hormone in young men: evidence for a central inhibitory action of ghrelin on the gonadal axis.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXhtFChurfL&md5=ea1cadefe5cf53630f1229ebdce35221CAS | 18559917PubMed |

Liu, J., Prudom, C. E., Nass, R., Pezzoli, S. S., Oliveri, M. C., Johnson, M. L., Veldhuis, P., Gordon, D. A., Howard, A. D., Witcher, D. R., Geysen, H. G., Gaylinn, B. D., and Thorner, M. O. (2008). Novel ghrelin assays provide evidence for independent regulation of ghrelin acylation and secretion in healthy young men. J. Clin. Endocrinol. Metab. 93, 1980–1987.
| 1:CAS:528:DC%2BD1cXlvFWgt70%3D&md5=594b3a856725507177a35a0fe10e0737CAS | 18349056PubMed |

Lorenzi, T., Meli, R., Marzioni, D., Morroni, M., Baragli, A., Castellucci, M., Gualillo, O., and Muccioli, G. (2009). Ghrelin: a metabolic signal affecting the reproductive system. Cytokine Growth Factor Rev. 20, 137–152.
Ghrelin: a metabolic signal affecting the reproductive system.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXktl2jtL8%3D&md5=81fd70739440d9e7176adb78274c5138CAS | 19297235PubMed |

Martini, A. C., Fernández-Fernández, R., Tovar, S., Navarro, V. M., Vigo, E., Vazquez, M. J., Davies, J. S., Thompson, N. M., Aguilar, E., Pinilla, L., Wells, T., Dieguez, C., and Tena-Sempere, M. (2006). Comparative analysis of the effects of ghrelin and unacylated ghrelin on luteinizing hormone secretion in male rats. Endocrinology 147, 2374–2382.
Comparative analysis of the effects of ghrelin and unacylated ghrelin on luteinizing hormone secretion in male rats.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XjvFOru7g%3D&md5=1162ed071c3796160b4f670cc3a0df8cCAS | 16455774PubMed |

Martos-Moreno, G. A., Chowen, J. A., and Argente, J. (2010). Metabolic signals in human puberty: effects of over and undernutrition. Mol. Cell. Endocrinol. 324, 70–81.
Metabolic signals in human puberty: effects of over and undernutrition.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXotVWqsr0%3D&md5=ecfbc001232fa8b60d8f11d66bb5e435CAS | 20026379PubMed |

Merriam, G. R., and Wachter, K. W. (1982). Algorithms for the study of episodic hormone secretion. Am. J. Physiol. 243, E310–E318.
| 1:CAS:528:DyaL38XlsFOhtrc%3D&md5=df2ff9a367a36e82a5673d0815da5138CAS | 6889816PubMed |

Messini, C. I., Dafopoulos, K., Chalvatzas, N., Georgoulias, P., and Messinis, I. E. (2009). Effect of ghrelin on gonadotrophin secretion in women during the menstrual cycle. Hum. Reprod. 24, 976–981.
Effect of ghrelin on gonadotrophin secretion in women during the menstrual cycle.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXjsFeksbk%3D&md5=5563e7ddaa9ce5a1526950cfa92f9248CAS | 19095668PubMed |

Meunier, H., Rivier, C., Evans, R. M., and Vale, W. (1988). Gonadal and extragonadal expression of inhibin α, β A and β B subunits in various tissues predict diverse functions. Proc. Natl. Acad. Sci. USA 85, 247–251.
Gonadal and extragonadal expression of inhibin α, β A and β B subunits in various tissues predict diverse functions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaL1cXhtVKksrs%3D&md5=680d9bd40ba3b585d835060aa69b620aCAS | 2829170PubMed |

Miller, D. W., Harrison, J. L., Brown, Y. A., Doyle, U., Lindsay, A., Adam, C. L., and Lea, R. G. (2005). Immunohistochemical evidence for an endocrine/paracrine role for ghrelin in the reproductive tissues of sheep. Reprod. Biol. Endocrinol. 3, 60–74.
Immunohistochemical evidence for an endocrine/paracrine role for ghrelin in the reproductive tissues of sheep.Crossref | GoogleScholarGoogle Scholar | 16259638PubMed |

Miura, H., Tsuchiya, N., Sasaki, I., Kikuchi, M., Kojima, M., Kangawa, K., Hasegawa, Y., and Ohnami, Y. (2004). Changes in plasma ghrelin and growth hormone concentrations in mature Holstein cows and three-month-old calves. J. Anim. Sci. 82, 1329–1333.
| 1:CAS:528:DC%2BD2cXjs1Grurs%3D&md5=279d3383eb30a68ddeb1cbd6b5da247aCAS | 15144072PubMed |

Muccioli, G., Lorenzi, T., Lorenzi, M., Ghè, C., Arnoletti, E., Raso, G. M., Castellucci, M., Gualillo, O., and Meli, R. (2011). Beyond the metabolic role of ghrelin: a new player in the regulation of reproductive function. Peptides 32, 2514–2521.
Beyond the metabolic role of ghrelin: a new player in the regulation of reproductive function.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXhsFOgtbjI&md5=c899404acd61b42abe3444ea4d2faf29CAS | 22074955PubMed |

NRC ‘Nutrient Requirements of Sheep’. 6th edn. (National Academy Press: Washington, DC.) 1985.

Ojeda, S. R., Dubay, C., Lomniczi, A., Kaidar, G., Matagne, V., Sandau, U. S., and Dissen, G. A. (2010a). Gene networks and the neuroendocrine regulation of puberty. Mol. Cell. Endocrinol. 324, 3–11.
Gene networks and the neuroendocrine regulation of puberty.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXotVWru7g%3D&md5=16766f9d636fe8b6e4b4bd17dee4ea2aCAS | 20005919PubMed |

Ojeda, S. R., Lomniczi, A., Sandau, U., and Matagne, V. (2010b). New concepts on the control of the onset of puberty. Endocr. Dev. 17, 44–51.
New concepts on the control of the onset of puberty.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXptlaisL8%3D&md5=902459066a9d087f4f3f172577f8190fCAS | 19955755PubMed |

Parent, A. S., Teilmann, G., Juul, A., Skakkebaek, N. E., Toppari, J., and Bourguignon, J. P. (2003). The timing of normal puberty and the age limits of sexual precocity: variations around the world, secular trends, and changes after migration. Endocr. Rev. 24, 668–693.
The timing of normal puberty and the age limits of sexual precocity: variations around the world, secular trends, and changes after migration.Crossref | GoogleScholarGoogle Scholar | 14570750PubMed |

Petersen, P. S., Woldbye, D. P., Madsen, A. N., Egerod, K. L., Jin, C., Lang, M., Rasmussen, M., Beck-Sickinger, A. G., and Holst, B. (2009). In vivo characterization of high basal signaling from the ghrelin receptor. Endocrinology 150, 4920–4930.
In vivo characterization of high basal signaling from the ghrelin receptor.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXhsVCht7nK&md5=589fbe3cb7246c20870623ca047ef47aCAS | 19819980PubMed |

Pfaffl, M. W. (2001). A new mathematical model for relative quantification in real-time RT-PCR. Nucleic Acids Res. 29, e45.
A new mathematical model for relative quantification in real-time RT-PCR.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD38nis12jtw%3D%3D&md5=51f6629ba1b312b1408f7eddf9237334CAS | 11328886PubMed |

Pfaffl, M. W., Horgan, G. W., and Dempfle, L. (2002). Relative Expression Software Tool (REST) for group-wise comparison and statistical analysis of relative expression results in real-time PCR. Nucleic Acids Res. 30, e36.
Relative Expression Software Tool (REST) for group-wise comparison and statistical analysis of relative expression results in real-time PCR.Crossref | GoogleScholarGoogle Scholar | 11972351PubMed |

Polkowska, J., Lerrant, Y., Wańkowska, M., Wójcik-Gładysz, A., Starzec, A., and Counis, R. (2003). The effect of dietary protein restriction on the secretion of LH and FSH in pre-pubertal female lambs. Anim. Reprod. Sci. 76, 53–66.
The effect of dietary protein restriction on the secretion of LH and FSH in pre-pubertal female lambs.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXmt1artQ%3D%3D&md5=d76fc33738ee2faa7887c0e7eecf0687CAS | 12559720PubMed |

Polkowska, J., Wańkowska, M., Romanowicz, K., Gajewska, A., Misztal, T., and Wójcik-Gładysz, A. (2011). The effect of intracerebroventricular infusion of ghrelin and/or short fasting on the gene expression and immunoreactivity of somatostatin in the hypothalamic neurons and on pituitary growth hormone in prepubertal female lambs. Brain Res. 1414, 41–49.
The effect of intracerebroventricular infusion of ghrelin and/or short fasting on the gene expression and immunoreactivity of somatostatin in the hypothalamic neurons and on pituitary growth hormone in prepubertal female lambs.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXhtFymu7%2FL&md5=b6a97db0793f293a9df9686fab64a732CAS | 21872221PubMed |

Polkowska, J., Gajewska, A., Wańkowska, M., Misztal, T., and Wójcik-Gładysz, A. (2012). The effect of intracerebroventricular infusions of ghrelin or short fasting on the gene expression and immunoreactivity of neuropeptide Y in the hypothalamic neurons in prepubertal female lambs: a morphofunctional study. J. Chem. Neuroanat. 46, 45–50.
The effect of intracerebroventricular infusions of ghrelin or short fasting on the gene expression and immunoreactivity of neuropeptide Y in the hypothalamic neurons in prepubertal female lambs: a morphofunctional study.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xhs1Sht7vL&md5=87610a11b98c1b653d063d6eab0160feCAS | 23085194PubMed |

Reichenbach, A., Steyn, F. J., Sleeman, M. W., and Andrews, Z. B. (2012). Ghrelin receptor expression and colocalization with anterior pituitary hormones using a GHSR-GFP mouse line. Endocrinology 153, 5452–5466.
Ghrelin receptor expression and colocalization with anterior pituitary hormones using a GHSR-GFP mouse line.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xhs1OnsLfM&md5=8c4470ac2aaeb76d205224888c321663CAS | 22962259PubMed |

Schaeffer, M., Langletd, F., Lafonta, C., Molinoa, F., Hodsona, D. J., Thomas-Rouxg, T., Lamarqueg, L., Verdiéh, P., Bourrierg, E., Dehouckd, B., Banèresh, J.-L., Martinezh, J., Mérya, P.-F., Marieh, J., Trinquetg, E., Fehrentzh, J.-A., Prévotd, V., and Mollard, P. (2013). Rapid sensing of circulating ghrelin by hypothalamic appetite-modifying neurons. Proc. Natl Acad. Sci. USA 110, 1512–1517.
Rapid sensing of circulating ghrelin by hypothalamic appetite-modifying neurons.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXhvFKrsro%3D&md5=c1f9a8a79882c29e39558faf484de0a8CAS | 23297228PubMed |

Schneeberger, M., Gomis, R., and Claret, M. (2014). Hypothalamic and brainstem neuronal circuits controlling homeostatic energy balance. J. Endocrinol. 220, T25–T46.
Hypothalamic and brainstem neuronal circuits controlling homeostatic energy balance.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXjtlSls7o%3D&md5=fdf4545b557c49b3acf605aefec78fefCAS | 24222039PubMed |

Snyder, J. L., Clapper, J. A., Roberts, A. J., Sanson, D. W., Hamernik, D. L., and Moss, G. E. (1999). Insulin-like growth factor-I, insulin-like growth factor-binding proteins, and gonadotropins in the hypothalamic-pituitary axis and serum of nutrient-restricted ewes. Biol. Reprod. 61, 219–224.
Insulin-like growth factor-I, insulin-like growth factor-binding proteins, and gonadotropins in the hypothalamic-pituitary axis and serum of nutrient-restricted ewes.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK1MXktFKgu7o%3D&md5=0bcbd325c7c3c5512f338c281cffa2dcCAS | 10377052PubMed |

Strzetelski, J. A., Brzóska, F., Kowalski, Z. M., and Osięgłowski, S. (2014). ‘Zalecenia Żywieniowe dla Przeżuwaczy i Tabele Wartości Pokarmowej Pasz’. (Instytut Zootechniki: Kraków.) [In Polish]

Stupnicki, R., and Kula, E. (1982). Direct radioimmunoassay of progesterone in human plasma. Endokrinologie 80, 1–7.
| 1:CAS:528:DyaL38XlvFehsLY%3D&md5=a6f5f3a0ec9ce7cc3431ff352dd9c0b7CAS | 7173117PubMed |

Sugino, T., Hasegawa, Y., Kikkawa, Y., Yamaura, J., Yamagishi, M., Kurose, Y., Kojima, M., Kangawa, K., and Terashima, Y. (2002). A transient ghrelin surge occurs just before feeding in a scheduled meal-fed sheep. Biochem. Biophys. Res. Commun. 295, 255–260.
A transient ghrelin surge occurs just before feeding in a scheduled meal-fed sheep.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38XltFers7o%3D&md5=7cb3438a6d5f270c2ba1839c1e7902e8CAS | 12150940PubMed |

The ESHRE Capri Workshop Group (2006). Nutrition and reproduction in women. Hum. Reprod. Update 12, 193–207.
Nutrition and reproduction in women.Crossref | GoogleScholarGoogle Scholar | 16449360PubMed |

Thomas, G. B., Mercer, J. E., Karalis, T., Rao, A., Cummins, J. T., and Clarke, I. J. (1990). Effect of restricted feeding on the concentrations of growth hormone (GH), gonadotropins and prolactin (PRL) in plasma and on the amounts of messenger ribonucleic acid for GH, gonadotropin subunits and PRL in the pituitary glands of adult ovariectomized ewes. Endocrinology 126, 1361–1367.
Effect of restricted feeding on the concentrations of growth hormone (GH), gonadotropins and prolactin (PRL) in plasma and on the amounts of messenger ribonucleic acid for GH, gonadotropin subunits and PRL in the pituitary glands of adult ovariectomized ewes.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK3cXhslOns7c%3D&md5=3f7f21f01e6214ccaab9ca51fceddbaaCAS | 2307109PubMed |

Traczyk, W., and Przekop, F. (1963). Methods of investigation of the function of the hypothalamus and hypophysis in chronic experiments in sheep. Acta Physiol. Pol. 14, 217–226.

Wahab, F., Shahab, M., and Behr, R. (2015). The involvement of gonadotropin inhibitory hormone and kisspeptin in the metabolic regulation of reproduction. J. Endocrinol. 225, R49–R66.
The involvement of gonadotropin inhibitory hormone and kisspeptin in the metabolic regulation of reproduction.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXhtFCmsLzO&md5=04c10ea53fd6a16685a7642a227175deCAS | 25957191PubMed |

Wang, L., Saint-Pierre, D. H., and Taché, Y. (2002). Peripheral ghrelin selectively increases Fos expression in neuropeptide Y-synthesizing neurons in mouse hypothalamic arcuate nucleus. Neurosci. Lett. 325, 47–51.
Peripheral ghrelin selectively increases Fos expression in neuropeptide Y-synthesizing neurons in mouse hypothalamic arcuate nucleus.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38XjvVeisbs%3D&md5=f62aba451dcdff07ff38096ecbb8e99aCAS | 12023064PubMed |

Wańkowska, M., Lerrant, Y., Wójcik-Gładysz, A., Starzec, A., Counis, R., and Polkowska, J. (2002). Intracerebroventricular infusion of neuropeptide Y up-regulates synthesis and accumulation of luteinizing hormone but not follicle stimulating hormone in the pituitary cells of prepubertal female lambs. J. Chem. Neuroanat. 23, 133–142.
Intracerebroventricular infusion of neuropeptide Y up-regulates synthesis and accumulation of luteinizing hormone but not follicle stimulating hormone in the pituitary cells of prepubertal female lambs.Crossref | GoogleScholarGoogle Scholar | 11841917PubMed |

Welento, J., Szteyn, S., and Milart, Z. (1969). Observations on the stereotaxic configuration of the hypothalamic nuclei in the sheep. Anat. Anz. 124, 1–27.
| 1:STN:280:DyaF1M3gs1Oisw%3D%3D&md5=74b6886f04b1f6ebf43ecdcb45612f96CAS | 4891518PubMed |

Wertz-Lutz, A. E., Knight, T. J., Pritchard, R. H., Daniel, J. A., Clapper, J. A., Smart, A. J., Trenkle, A., and Beitz, D. C. (2006). Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle. J. Anim. Sci. 84, 3285–3300.
Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28Xht1CnurnP&md5=d0ef41c864051e3b3552f3656bc53ce2CAS | 17093221PubMed |

Wójcik-Gładysz, A., Wańkowska, M., Gajewska, A., Misztal, T., Szlis, M., and Polkowska, J. (2014). The effect of intracerebroventricular infusions of ghrelin on the secretory activity of the GnRH/LH system in peripubertal female sheep. J. Anim. Feed Sci. 23, 299–308.

Zigman, J. M., Jones, J. E., Lee, C. E., Saper, C. B., and Elmquist, J. K. (2006). Expression of ghrelin receptor mRNA in the rat and the mouse brain. J. Comp. Neurol. 494, 528–548.
Expression of ghrelin receptor mRNA in the rat and the mouse brain.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD28XktVeltQ%3D%3D&md5=c9d84a55a309586b5856f0bb668aed6bCAS | 16320257PubMed |

Zizzari, P., Hassouna, R., Longchamps, R., Epelbaum, J., and Tolle, V. (2011). Meal anticipatory rise in acylated ghrelin at dark onset is blunted after long-term fasting in rats. J. Neuroendocrinol. 23, 804–814.
Meal anticipatory rise in acylated ghrelin at dark onset is blunted after long-term fasting in rats.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXhtFaqsLvM&md5=f891bd1ccfa2acf08ce42b63ea0bc29eCAS | 21722214PubMed |