The effect of orexin B receptor antagonist and steroid hormones on milk lactose synthesis in the lactating rats

Document Type : Research Paper


Department of Animal Sciences and Marine Biology, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran


Background and Objective: Prolactin is a necessary factor for lactation and synthesis of milk constituent. Progesterone (P4) and 17β-estradiol (E2) are inhibitory factors for lactation. Orexin is involved in regulating the metabolism and lipid synthesis. Present study investigated the orexin B receptor antagonist and steroid hormone effects on milk lactose synthesis.
Materials and Methods: Thirty Wistar lactating rats were used. Lactating animals in the group 1-4 received saline, 1, 2 or 4 µg of orexin antagonist. Lactating animals of the groups 5 and 6 received 4 µg of orexin antagonist plus 1 µg of 17-β estradiol (E2) or 4 mg of progesterone (p4). Blood and tissue samples were collected at 60 and 180 minutes of injections. Blood samples were measured for prolactin concentrations and tissue samples were examined for alpha lactalbumin (Lalba) and beta-1,4-galactosyltransferase 1 (B4galt1) gene expression in the mammary gland by RT-PCR technique.
Results: Injection of orexin antagonist significantly increased the percentage of milk lactose, plasma prolactin and Lalba gene expression in comparison to control group. Injections of E2 or P4 inhibited the increased effects of orexin antagonist on mean milk lactose percentage, prolactin and Lalba gene expression in comparison to orexin antagonist group. Injections of all drugs did not alter the mean B4galt1 gene expression.
Conclusion: Stimulatory effects of orexin antagonist on milk production may be partly due to the increased prolactin concentration and Lalba gene expression. The mechanism by which the steroid hormones supress the orexin antagonist-induced lactose synthesis may be mediated partly via inhibiting the prolactin production.


  1. Liu H, Zhao K, Liu J. Effects of glucose availability on expression of the key genes involved in synthesis of milk fat, lactose and glucose metabolism in bovine mammary epithelial cells. PloS one 2013; 8(6): e66092.
  2. Sadovnikova A, Garcia SC, Hovey RC. A comparative review of the cell biology, biochemistry, and genetics of lactose synthesis. Journal of Mammary Gland Biology and Neoplasia 2021; (2):181-96.
  1. Lin Y, Sun X, Hou X, Qu B, Gao X, Li Q. Effects of glucose on lactose synthesis in mammary epithelial cells from dairy cow. BMC Veterinary Research 2016; 12:1-1.
  2. Russell SH, Kim MS, Small CJ, Abbott CR, Morgan DG, Taheri S, Murphy KG, Todd JF, Ghatei MA, Bloom SR. Central administration of orexin A suppresses basal and domperidone stimulated plasma prolactin. Journal of neuroendocrinology 2000;12(12):1213-8.
  3. Liu L, Wang Q, Liu A, Lan X, Huang Y, Zhao Z, Jie H, Chen J, Zhao Y. Physiological implications of orexins/hypocretins on energy metabolism and adipose tissue development. ACS omega 2019;5(1):547-55.
  4. Milbank E, López M. Orexins/hypocretins: key regulators of energy homeostasis. Frontiers in Endocrinology 2019; 10:830.
  5. Garmkhani SB, Khazali H. Breast Intra-Ductal Injection of Orexin-A receptor antagonist (SB-334867-A) Decreases Gene Expression of Mammary Lipogenic Enzymes and Insulin Serum Levels in the Lactating rats. Novelty in Biomedicine.;10(3):152-8.
  6. Khazali H. The Effects of Intra-Ductal Mammary Administration of Orexin-A Antagonist (SB-334867) on the PPARγ and SREBP1c Gene Expression and Serum Adiponectin Levels in Lactating Rats. International Journal of Basic Science in Medicine 2022;7(1):15-20.
  7. Tong JJ, Thompson IM, Zhao X, Lacasse P. Effect of 17β-estradiol on milk production, hormone secretion, and mammary gland gene expression in dairy cows. Journal of Dairy Science 2018 ;101(3):2588-601.
  8. Kochenour NK. Lactation suppression Clin Obstet Gynecol 1980;23(4):1045-59.
  9. Capuco AV, Akers RM. The origin and evolution of lactation. Journal of Biology 2009 ;8:1-4.
  10. Misztal T, Molik E, Nowakowski M, Marciniak E. Milk yield, lactation parameters and prolactin secretion characteristics in sheep treated with melatonin implants during pregnancy and lactation in long-day conditions. Livestock science 2018; 218:58-64.
  11. Yang H, Yan M, Cheng C, Jiang J, Zhang L, Liu J, Zhou Z, Shen A. Expression of β‐1, 4‐galactosyltransferase I in rat Schwann cells. Journal of cellular biochemistry 2009;108(1):75-86.
  12. Crisà A, Claps S, Moioli B, Marchitelli C. Identification of the complete coding cDNAs and expression analysis of B4GALT1, LALBA, ST3GAL5, ST6GAL1 in the colostrum and milk of the Garganica and Maltese goat breeds to reveal possible implications for oligosaccharide biosynthesis. BMC Veterinary Research 2019;15(1):1-4.
  1. Mahmoudi F, Gollo KH. Influences of serotonin hydrochloride on Adiponectin, Ghrelin and KiSS1 genes expression. Galen Medical Journal 2020;9: e1767.
  2. Fujisawa S, Komatsubara M, Ogura-Ochi K, Tsukamoto-Yamauchi N, Toma K, Inagaki K, Wada J, Otsuka F. Orexin A modulates prolactin production by regulating BMP-4 activity in rat pituitary lactotorope cells. Peptides 2019; 113:35-40.
  3. Lyons DJ, Hellysaz A, Ammari R, Broberger C. Hypocretin/orexin peptides excite rat neuroendocrine dopamine neurons through orexin 2 receptor-mediated activation of a mixed cation current. Scientific Reports 2017;7(1):41535.
  4. Garcia MC, Lopez M, Gualillo O, Seoane LM, Dieguez C, Señarís RM. Hypothalamic levels of NPY, MCH, and prepro‐orexin mRNA during pregnancy and lactation in the rat: role of prolactin. The FASEB journal 2003;17(11):1392-400.
  5. Wang JB, Murata T, Narita K, Honda K, Higuchi T. Variation in the expression of orexin and orexin receptors in the rat hypothalamus during the estrous cycle, pregnancy, parturition, and lactation. Endocrine 2003; 22:127-34.
  6. Turkington RW, Hill RL. Lactose synthetase: progesterone inhibition of the induction of α-lactalbumin. Science 1969;163(3874):1458-60.
  7. Shin HY, Hennighausen L, Yoo KH. STAT5-driven enhancers tightly control temporal expression of mammary-specific genes. Journal of mammary gland biology and neoplasia 2019 ;24:61-71.
  8. Kleinberg DL, Todd J, Babitsky G. Inhibition by estradiol of the lactogenic effect of prolactin in primate mammary tissue: reversal by antiestrogens LY 156758 and tamoxifen. Proceedings of the National Academy of Sciences 1983;80(13):4144-8.
  9. Deis RP, Delouis C. Lactogenesis induced by ovariectomy in pregnant rats and its regulation by oestrogen and progesterone. Journal of steroid biochemistry 1983;18(6):687-90.
  10. Grafe LA, Bhatnagar S. Orexins and stress. Front Neuroendocrinol 2018; 51: 132–145.
  1. Trivedi P, Yu H, MacNeil DJ, Van der Ploeg LH, Guan XM. Distribution of orexin receptor mRNA in the rat brain. FEBS letters 1998;438(1-2):71-5.
  2. Grafe LA, Eacret D, Luz S, Gotter AL, Renger JJ, Winrow CJ, Bhatnagar S. Orexin 2 receptor regulation of the hypothalamic–pituitary–adrenal (HPA) response to acute and repeated stress. Neuroscience 2017; 348:313-23.
  3. Ponchon B, Zhao X, Ollier S, Lacasse P. Relationship between glucocorticoids and prolactin during mammary gland stimulation in dairy cows. Journal of Dairy Science 2017;100(2):1521-34.
  4. Llopis J, Lampreabe A, Peran F, Mataix FJ, Urbano G, Montellano MA. Influence of hydrocortisone acetate administered to the lactating rat on lipid composition of the milk and serum lipid levels in dams and pups. Hormone and metabolic research 1989;21(08):421-6.
  5. Lee DY, Kim E, Choi MH. Technical and clinical aspects of cortisol as a biochemical marker of chronic stress. BMB Rep2015; 48:209–16