Analgesic effect of trans-anethole via downregulation of hypothalamic orexin and melanin-concentrating hormone gene expression in the rat

Document Type : Research Paper


Department of Biology, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iran



Background and Objective: The role of the central nervous system in pain control is prominent via the regulation of neuropeptides. Plant derivatives such as trans-anethole could be effective due to analgesic properties. The present study investigated the analgesic effect of trans-anethole via modulation of hypothalamic orexin and melanin-concentrating hormone (MCH) gene expression in rats.
Materials and Methods: Twenty male Wistar rats (180-200 g) grouped into four groups of five rats (n=5). To induce pain, 50 μl of formalin was injected into the hind paws of the animals. The intact and formalin control groups received saline. Formalin induced pain groups received 150 or 250 mg/kg of trans-anethole. Pain score was evaluated by performing the formalin test. The hypothalamic samples were removed to analyze the gene expression levels via real-time PCR technique.
Results: The pain score decreased in rats receiving 150 or 250 mg/kg trans-anethole compared to formalin control group. The relative gene expression of Orexin and MCH significantly increased in the formalin group compared to the intact rats. Injection of 150 or 250 mg/kg trans-anethole significantly reduced the relative gene expression of orexin and MCH in formalin induced pain groups compared to the formalin control rats.
Conclusion: Trans anethole caused downregulation of hypothalamic orexin and MCH gene expression due to its pain relieving properties. So, analgesic effects of trans anethole may be mediated via central mechanism.


  1. Alshami AM. Pain: Is it all in the brain or the heart?. Current Pain and Headache Reports 2019; 23:1-4.
  2. Lavand’homme P. The progression from acute to chronic pain. Current Opinion in Anesthesiology 2011;24(5):545-50.
  3. Ezzatpanah S, Babapour V, Sadeghi B, Haghparast A. Chemical stimulation of the lateral hypothalamus by carbachol attenuated the formalin-induced pain behaviors in rats. Pharmacology Biochemistry and Behavior 2015; 129:105-10.
  4. Wang D, Pan X, Zhou Y, Wu Z, Ren K, Liu H, Huang C, Yu Y, He T, Zhang X, Yang L. Lateral septum-lateral hypothalamus circuit dysfunction in comorbid pain and anxiety. Molecular Psychiatry 2023; 16:1-1.
  5. Jang JH, Park JY, Oh JY, Bae SJ, Jang H, Jeon S, Kim J, Park HJ. Novel analgesic effects of melanin-concentrating hormone on persistent neuropathic and inflammatory pain in mice. Scientific Reports 2018; 8(1):707.
  6. Lin Y, Quartermain D, Dunn AJ, Weinshenker D, Stone EA. Possible dopaminergic stimulation of locus coeruleus α1‐adrenoceptors involved in behavioral activation. Synapse 2008; 62(7):516-23.
  7. Hooten WM. Chronic pain and mental health disorders: shared neural mechanisms, epidemiology, and treatment. InMayo Clinic Proceedings 2016; 91(7):955-970.
  8. Mahboubi M. Foeniculum vulgare as valuable plant in management of women's health. Journal of menopausal medicine 2019;25(1):1-4.
  9. Martins, I. et al. Noradrenaline increases pain facilitation from the brain during inflammatory pain. Neuropharmacology 2013; 71: 299–307.
  10. Memon T, Yarishkin O, Reilly CA, Križaj D, Olivera BM, Teichert RW. trans-Anethole of fennel oil is a selective and nonelectrophilic agonist of the TRPA1 ion channel. Molecular Pharmacology 2019; 95(4):433-41.
  11. Mesfin M, Asres K, Shibeshi W. Evaluation of anxiolytic activity of the essential oil of the aerial part of Foeniculum vulgare Miller in mice. BMC complementary and alternative medicine 2014;14(1):1-7
  12. Borgland SL, Taha SA, Sarti F, Fields HL, Bonci A. Orexin A in the VTA is critical for the induction of synaptic plasticity and behavioral sensitization to cocaine. Neuron 2006;49(4):589-601.
  1. Boutrel B, Kenny PJ, Specio SE, Martin-Fardon R, Markou A, Koob GF, de Lecea L. Role for hypocretin in mediating stress-induced reinstatement of cocaine-seeking behavior. Proceedings of the National Academy of Sciences 2005;102(52):19168-73.
  2. Camurça-Vasconcelos AL, Bevilaqua CM, Morais SM, Maciel MV, Costa CT, Macedo IT, Oliveira LM, Braga RR, Silva RA, Vieira LS. Anthelmintic activity of Croton zehntneri and Lippia sidoides essential oils. Veterinary Parasitology 2007 ;148(3-4):288-94.
  3. Ritter AM, Ames FQ, Otani F, de Oliveira RM, Cuman RK, Bersani-Amado CA. Effects of anethole in nociception experimental models. Evidence-Based Complementary and Alternative Medicine 2014 ; 1-7.
  4. Vastegani SM, Khoshnam SE, Mansouri E, Hajipour S, Ghafouri S, Bakhtiari N, Sarkaki A, Farbood Y. Neuroprotective effect of anethole against rotenone induced non-motor deficits and oxidative stress in rat model of Parkinson’s disease. Behavioural Brain Research 2023; 437:100-114.
  5. Melo Júnior JD, Damasceno MD, Santos SA, Barbosa TM, Araújo JR, Vieira-Neto AE, Wong DV, Lima-Júnior RC, Campos AR. Acute and neuropathic orofacial antinociceptive effect of eucalyptol. Inflammopharmacology 2017; 25:247-54.
  6. Radmehr M, Jahromi HK, Abedi H, Seifi V, Karami S, Jahromi ZK. Comparison of the effect of lycopene with ibuprofen on sensory threshold of pain using formalin test in adult male rats. Journal of Chemical and Pharmaceutical Research 2016; 8(4):1322-7.
  7. Asadian M, Yaghoubi H, Mahmoudi F, Gollo KH. Effect of Trans-Anethole on Gene Expression of Steroidogenic Enzymes in the Ovary of Polycystic Ovary Syndrome Model Rate. Galen Medical Journal 2022;11: e2219.
  8. Meymandi MS, Sepehri G, Izadi G, Zamiri Z. Evidence for antinociceptive effects of combined administration of vitamin E and celecoxib in tail-flick and formalin test in male rats. Pharmacological Reports 2019; 71(3):457-64.
  9. Fountas A, Van Uum S, Karavitaki N. Opioid-induced endocrinopathies. The Lancet Diabetes & Endocrinology 2020; 8(1):68-80.
  10. Wang B, Zhang G, Yang M, Liu N, Li YX, Ma H, Ma L, Sun T, Tan H, Yu J. Neuroprotective effect of anethole against neuropathic pain induced by chronic constriction injury of the sciatic nerve in mice. Neurochemical research 2018; 43:2404-22.
  1. Tas A, Ozbek H, ATASOY N, Altug M, CEYLAN E. Evaluation of analgesic and anti-inflammatory activity of Pimpinella anisum fixed oil extract. Indian Veterinary Journal 2006;83(8).
  2. Choi EM, Hwang JK. Antiinflammatory, analgesic and antioxidant activities of the fruit of Foeniculum vulgare. Fitoterapia 2004; 75(6):557-65.
  3. Elizabeth AA, Josephine G, Muthiah NS, Muniappan M. Evaluation of analgesic and anti-inflammatory effect of Foeniculum vulgare. Res. J. Pharm. Biol. Chem. Sci 2014; 5:658-68.
  4. Fakhoury M, Salman I, Najjar W, Merhej G, Lawand N. The lateral hypothalamus: an uncharted territory for processing peripheral neurogenic inflammation. Frontiers in neuroscience 2020; 14:101.
  5. Zhou W, Cheung K, Kyu S, Wang L, Guan Z, Kurien PA, Bickler PE, Jan LY. Activation of orexin system facilitates anesthesia emergence and pain control. Proceedings of the National Academy of Sciences. 2018;115(45): E10740-7.
  6. Jeong Y, Wagner MA, Ploutz-Snyder RJ, Holden JE. Pain condition and sex differences in the descending noradrenergic system following lateral hypothalamic stimulation. IBRO reports 2020; 8:11-7.
  7. Jahangirvand M, Yazdi F, Moradi M, Haghparast A. Intra-accumbal orexin-1 receptors are involved in antinociception induced by stimulation of the lateral hypothalamus in the formalin test as an animal model of persistent inflammatory pain. Iranian Journal of Pharmaceutical Research: IJPR 2016;15(4):851.
  8. Bomholt SF, Harbuz MS, Blackburn-Munro G, Blackburn-Munro RE. Involvement and role of the hypothalamo-pituitary-adrenal (HPA) stress axis in animal models of chronic pain and inflammation. Stress 2004;7(1):1-4.
  9. Kim KY, Lee HS, Seol GH. Anti-inflammatory effects of trans-anethole in a mouse model of chronic obstructive pulmonary disease. Biomedicine & Pharmacotherapy 2017; 91:925-30.
  10. Vgontzas AN, Fernandez‐Mendoza J, Lenker KP, Basta M, Bixler EO, Chrousos GP. Hypothalamic–pituitary–adrenal (HPA) axis response to exogenous corticotropin‐releasing hormone (CRH) is attenuated in men with chronic insomnia. Journal of Sleep Research 2022;31(3): e13526.
  1. Murala S, Nagarajan E, Bollu PC. Galanin, Substance P, and Melanin-Concentrating Hormone. In Neurochemistry in Clinical Practice 2022; 255-263.
  2. He X, Li Y, Zhang N, Huang J, Ming X, Guo R, Hu Y, Ji P, Guo F. Melanin-concentrating hormone promotes anxiety and intestinal dysfunction via basolateral amygdala in mice. Frontiers in Pharmacology 2022;13.
  3. Negahdari FM, Gholamnezhad Z, Noshahr ZS, Keshavarzi Z. A comparison between the effect of trans-anethole and metformin on biochemical parameters of polycystic ovary syndrome in rats. Avicenna Journal of Phytomedicine 2021;11(5):484.
  4. Zhang W, Wu H, Xu Q, Chen S, Sun L, Jiao C, Wang L, Fu F, Feng Y, Qian X, Chen X. Estrogen modulation of pain perception with a novel 17β-estradiol pretreatment regime in ovariectomized rats. Biology of sex Differences 2020; 11:1-3.