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《农业科学学报：英文版》
>Effects of Orexin A on mRNA Expression of Various Neuropeptides in the Hypothalamus and Pituitary, and on Serum LH Levels in Ovariectomized Gilts
Effects of Orexin A on mRNA Expression of Various Neuropeptides in the Hypothalamus and Pituitary, and on Serum LH Levels in Ovariectomized Gilts
Orexin has several biological functions, including the regulation of reproductive endocrine signaling, which has received much attention. However, little is known about the mechanism through which orexin regulates the levels of neuroendocrine hormones and peptides. We injected orexin A or physiological saline into the lateral ventricle of 10 ovariectomized (OVX) gilts, and determined the subsequent changes in serum luteinizing hormone (LH) concentration by using radioimmunoassay (RIA). We also examined the expression of GnRH, NPY, and POMC mRNAs in the hypothalamus and that of LH, follicle-stimulating hormone (FSH), POMC, and ghrelin mRNAs in the pituitary by using semi-quantitative reverse transcription polymerase chain reaction. We found the following results: (1) Orexin A transiently promoted LH secretion; serum LH concentration started to increase at 10 min after the orexin injection, peaked at 30 min, and returned to its initial level at 1.5 h; (2) orexin A upregulated GnRH mRNA expression and downregulated NPY and POMC mRNAs expression in the hypothalamus; (3) orexin A upregulated LH and FSH mRNAs expression (FSH, P > 0.05), but downregulated ghrelin mRNA expression in the pituitary. No significant effects were observed on the pituitary expression of FSH and POMC mRNAs. Our data suggest that orexin A regulates reproductive function by stimulating GnRH and LH release directly and indirectly via its effects on NPY, POMC and ghrelin expression.
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