Effects of central orexin A on gonadotropins and progesterone secretion in ewes during the luteal phase of the estrous cycle and during anestrus
Katarzyna Kirsz , Małgorzata Szczęsna , Aneta Bocheńska , Agnieszka Pietsch-Fulbiszewska , Natalia Sowińska , Natalia Kabała , Dorota Zięba-Przybylska
AbstractPrior studies, mainly on rodents demonstrated that orexin A (OXA) plays an important role in regulating the hypothalamo-pituitary-gonadal (HPG) axis. However, the results of those works have indicated that the central impact of OXA on the HPG axis may vary depending on the species or sex of the animal, the phase of the estrous cycle, or the experimental model system (in vivo vs. in vitro). The aim of the present study was to further investigate the role of OXA in the regulation of reproduction in seasonally breeding, intact, non-steroid-primed ewes during the luteal phase of the estrous cycle and during anestrus. We examined the effect of fourth-ventricle injections of OXA (0.3 μg/kg body weight) on plasma luteinizing hormone (LH), follicle-stimulating hormone (FSH) and progesterone concentrations and on the level of gonadotropin-releasing hormone receptor (GnRH-R) protein in the anterior pituitary (AP). Radioimmunoassays revealed that OXA treatments inhibited (P < 0.001) LH and FSH secretion during both examined periods and progesterone (P < 0.001) during the luteal phase. The influence of OXA on LH and FSH release may be partially attributable to the additional response of the pituitary to OXA, as, under the influence of OXA, the concentration of GnRH-R protein in the AP was downregulated during the luteal phase (P < 0.01) and during anestrus (P < 0.05). We conclude that OXA may be a negative regulator of gonadotropin secretion in intact, non-steroid-primed ewes in periods when the HPG axis is suppressed by negative feedback through steroid sex hormones.
|Journal series||Small Ruminant Research, ISSN 0921-4488, e-ISSN 1879-0941, (N/A 100 pkt)|
|Publication size in sheets||0.5|
|Keywords in English||Orexin A, Luteinizing hormone, Follicle-stimulating hormone, Progesterone, Gonadotropin-releasing hormone receptor, Intact and non-steroid-primed ewes|
|Publication indicators||= 0; : 2016 = 0.947; : 2018 = 1.21 (2) - 2018=1.351 (5)|
|Finansowanie||This work was supported by grunt from the H. Kołłątaj University of Agriculture in Krakow, Poland [grant number BM-4269/KBZ/2017].|
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