Original Article: The effect of orexin-2 and endocannabinoid-1 antagonists on neuronal activity of hippocampal CA1 pyramidal neurons in response to tramadol in rats


Department of Physiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran


Background: CA1, as a major structure involved in learning and memory, has been shown to be affected by tramadol addiction. Both orexin and endocannabinoid receptors express in CA1 and play an important role in drug dependency. The aim of this study was to evaluate the modulatory effects of orexin-2 (OX2R) and endocannabinoid-1 (CB1R) receptors on neuronal activity in CA1, in response to tramadol in rats. Materials and Methods: Male Wistar rats were divided into 8 groups (n = 6–7); saline-dimethyl sulfoxide (DMSO), tramadol-DMSO, saline-TCS-OX2-29, saline-AM251, tramadol-TCS-OX2-29, tramadol-AM251, saline-TCS-OX2-29-AM251, tramadol-TCS-OX2-29-AM251. Tramadol was injected intraperitoneally, and then, AM251 (1 nmol/0.3 μL), CB1R antagonist and TCS-OX2-29 (1 nmol/0.3 μL), OX2R antagonist, were microinjected individually or concurrently into the CA1. Using in vivo extracellular single-unit recording, the firing of CA1 pyramidal neurons was investigated. Results: Tramadol decreased neuronal activity in CA1 (P < 0.01) but increased it after micro-injection of DMSO. TCS-OX2-29 increased neuronal activity in saline group (P < 0.05) but decreased it in tramadol group. AM251 had no effect on saline group but decreased neuronal activity in tramadol group (P < 0.05). Concurrent micro-injection of TCS-OX2-29 and AM251 had no effect on saline group but decreased neuronal activity in tramadol group (P < 0.05). Conclusions: Our findings suggest that neural activity in CA1 is rapidly affected by acute use of tramadol, and some of these effects may be induced through the endocannabinoid and orexin systems. Thus, the function of endocannabinoid and orexin systems in CA1 may play a role in tramadol addiction.


Vazzana M, Andreani T, Fangueiro J, Faggio C, Silva C, Santini A, et al. Tramadol hydrochloride: Pharmacokinetics, pharmacodynamics, adverse side effects, co-administration of drugs and new drug delivery systems. Biomed Pharmacother 2015;70:234-8.  Back to cited text no. 1
Lee J, Yoo HD, Bae JW, Lee S, Shin KH. Population pharmacokinetic analysis of tramadol and O-desmethyltramadol with genetic polymorphism of CYP2D6. Drug Des Devel Ther 2019;13:1751-61.  Back to cited text no. 2
Miotto K, Cho AK, Khalil MA, Blanco K, Sasaki JD, Rawson R. Trends in tramadol: Pharmacology, metabolism, and misuse. Anesth Analg 2017;124:44-51.  Back to cited text no. 3
Faria J, Barbosa J, Moreira R, Queirós O, Carvalho F, Dinis-Oliveira RJ. Comparative pharmacology and toxicology of tramadol and tapentadol. Eur J Pain 2018;22:827-44.  Back to cited text no. 4
Lassen D, Damkier P, Brøsen K. The pharmacogenetics of tramadol. Clin Pharmacokinet 2015;54:825-36.  Back to cited text no. 5
Jafari-Sabet M, Jafari-Sabet AR, Dizaji-Ghadim A. Tramadol state-dependent memory: Involvement of dorsal hippocampal muscarinic acetylcholine receptors. Behav Pharmacol 2016;27:470-8.  Back to cited text no. 6
Nazari-Serenjeh F, Zarrabian S, Azizbeigi R, Haghparast A. Effects of dopamine D1- and D2-like receptors in the CA1 region of the hippocampus on expression and extinction of morphine-induced conditioned place preference in rats. Behav Brain Res 2021;397:112924.  Back to cited text no. 7
Asari Y, Ikeda Y, Tateno A, Okubo Y, Iijima T, Suzuki H. Acute tramadol enhances brain activity associated with reward anticipation in the nucleus accumbens. Psychopharmacology (Berl) 2018;235:2631-42.  Back to cited text no. 8
Niknamfar S, Nouri Zadeh-Tehrani S, Sadat-Shirazi MS, Akbarabadi A, Rahimi-Movaghar A, Zarrindast MR. μ-Opioid receptor in the CA1 involves in tramadol and morphine cross state-dependent memory. Neurosci Lett 2019;705:177-82.  Back to cited text no. 9
Soltesz I, Losonczy A. CA1 pyramidal cell diversity enabling parallel information processing in the hippocampus. Nat Neurosci 2018;21:484-93.  Back to cited text no. 10
Hamilton DJ, White CM, Rees CL, Wheeler DW, Ascoli GA. Molecular fingerprinting of principal neurons in the rodent hippocampus: A neuroinformatics approach. J Pharm Biomed Anal 2017;144:269-78.  Back to cited text no. 11
Müller C, Remy S. Septo-hippocampal interaction. Cell Tissue Res 2018;373:565-75.  Back to cited text no. 12
Bezaire MJ, Soltesz I. Quantitative assessment of CA1 local circuits: Knowledge base for interneuron-pyramidal cell connectivity. Hippocampus 2013;23:751-85.  Back to cited text no. 13
Kouvaros S, Papatheodoropoulos C. Major dorsoventral differences in the modulation of the local CA1 hippocampal network by NMDA, mGlu5, adenosine A2A and cannabinoid CB1 receptors. Neuroscience 2016;317:47-64.  Back to cited text no. 14
Hooshmandi M, Hosseinmardi N, Janahmadi M, Motamedi F, Elahi Mahani A, Sadat Aghamiri FF. The role of hippocampal orexin-1 receptors (OX1R) in mediating the effect of morphine on CA1 baseline synaptic response and short term synaptic plasticity. Journal of Arak University of Medical Sciences 2014;17:84-95.  Back to cited text no. 15
Fartootzadeh R, Azizi F, Alaei H, Reisi P. Orexin type-2 receptor blockade prevents the nicotine-induced excitation of nucleus accumbens core neurons in rats: An electrophysiological perspective. Pharmacol Rep 2019;71:361-6.  Back to cited text no. 16
Zhang XY, Yu L, Zhuang QX, Zhu JN, Wang JJ. Central functions of the orexinergic system. Neurosci Bull 2013;29:355-65.  Back to cited text no. 17
Edalat P, Kavianpour M, Zarrabian S, Haghparast A. Role of orexin-1 and orexin-2 receptors in the CA1 region of hippocampus in the forced swim stress- and food deprivation-induced reinstatement of morphine seeking behaviors in rats. Brain Res Bull 2018;142:25-32.  Back to cited text no. 18
Li SB, Jones JR, de Lecea L. Hypocretins, neural systems, physiology, and psychiatric disorders. Curr Psychiatry Rep 2016;18:7.  Back to cited text no. 19
Mackie K. Cannabinoid receptors: Where they are and what they do. J Neuroendocrinol 2008;20 Suppl 1:10-4.  Back to cited text no. 20
Santana F, Sierra RO, Haubrich J, Crestani AP, Duran JM, de Freitas Cassini L, et al. Involvement of the infralimbic cortex and CA1 hippocampal area in reconsolidation of a contextual fear memory through CB1 receptors: Effects of CP55,940. Neurobiol Learn Mem 2016;127:42-7.  Back to cited text no. 21
Borgelt LM, Franson KL, Nussbaum AM, Wang GS. The pharmacologic and clinical effects of medical cannabis. Pharmacotherapy 2013;33:195-209.  Back to cited text no. 22
Ozdemir E. The role of the cannabinoid system in opioid analgesia and tolerance. Mini Rev Med Chem 2020;20:875-85.  Back to cited text no. 23
Azizi F, Fartootzadeh R, Alaei H, Reisi P. Electrophysiological study of the response of ventral tegmental area non-dopaminergic neurons to nicotine after concurrent blockade of orexin receptor-2 and cannabinoid receptors-1. Brain Res 2019;1719:176-82.  Back to cited text no. 24
Fartootzadeh R, Azizi F, Alaei H, Reisi P. Functional crosstalk of nucleus accumbens CB1 and OX2 receptors in response to nicotine-induced place preference. Neurosci Lett 2019;698:160-4.  Back to cited text no. 25
Cannon CZ, Kissling GE, Hoenerhoff MJ, King-Herbert AP, Blankenship-Paris T. Evaluation of dosages and routes of administration of tramadol analgesia in rats using hot-plate and tail-flick tests. Lab Anim (NY) 2010;39:342-51.  Back to cited text no. 26
Azizi F, Fartootzadeh R, Alaei H, Reisi P. Effects of concurrent blockade of OX2 and CB1 receptors in the ventral tegmental area on nicotine-induced place preference in rats. Neurosci Lett 2018;684:121-6.  Back to cited text no. 27
Paxinos G, Watson C. The rat brain in stereotaxic coordinates. Fifth ed. San Diego: Academic Press; 2005.  Back to cited text no. 28
Fogaça MV, Sonego AB, Rioli V, Gozzo FC, Dale CS, Ferro ES, et al. Anxiogenic-like effects induced by hemopressin in rats. Pharmacol Biochem Behav 2015;129:7-13.  Back to cited text no. 29
Chen XY, Chen L, Du YF. Orexin-A increases the firing activity of hippocampal CA1 neurons through orexin-1 receptors. J Neurosci Res 2017;95:1415-26.  Back to cited text no. 30
Riahi E, Arezoomandan R, Fatahi Z, Haghparast A. The electrical activity of hippocampal pyramidal neuron is subjected to descending control by the brain orexin/hypocretin system. Neurobiol Learn Mem 2015;119:93-101.  Back to cited text no. 31
Kutlu MG, Gould TJ. Effects of drugs of abuse on hippocampal plasticity and hippocampus-dependent learning and memory: Contributions to development and maintenance of addiction. Learn Mem 2016;23:515-33.  Back to cited text no. 32
Xiao Z, Lin K, Fellous JM. Conjunctive reward-place coding properties of dorsal distal CA1 hippocampus cells. Biol Cybern 2020;114:285-301.  Back to cited text no. 33
Zarrindast MR. Neurotransmitters and cognition. EXS 2006;98:5-39.  Back to cited text no. 34
Fasano C, Rocchetti J, Pietrajtis K, Zander JF, Manseau F, Sakae DY, et al. Regulation of the hippocampal network by VGLUT3-positive CCK- GABAergic basket cells. Front Cell Neurosci 2017;11:140.  Back to cited text no. 35
Jafari-Sabet M, Mofidi H, Attarian-Khosroshahi MS. NMDA receptors in the dorsal hippocampal area are involved in tramadol state-dependent memory of passive avoidance learning in mice. Can J Physiol Pharmacol 2018;96:45-50.  Back to cited text no. 36
El-Hamid Mohamed Elwy A, Tabl G. Impact of tramadol and morphine abuse on the activities of acetylcholine esterase, Na+/K+-ATPase and related parameters in cerebral cortices of male adult rats. Electron Physician 2017;9:4027-34.  Back to cited text no. 37
Bloms-Funke P, Dremencov E, Cremers TI, Tzschentke TM. Tramadol increases extracellular levels of serotonin and noradrenaline as measured by in vivo microdialysis in the ventral hippocampus of freely-moving rats. Neurosci Lett 2011;490:191-5.  Back to cited text no. 38
Tada K, Kasamo K, Ueda N, Suzuki T, Kojima T, Ishikawa K. Anxiolytic 5-hydroxytryptamine1A agonists suppress firing activity of dorsal hippocampus CA1 pyramidal neurons through a postsynaptic mechanism: Single-unit study in unanesthetized, unrestrained rats. J Pharmacol Exp Ther 1999;288:843-8.  Back to cited text no. 39
Buhot MC, Martin S, Segu L. Role of serotonin in memory impairment. Ann Med 2000;32:210-21.  Back to cited text no. 40
Ogren SO, Eriksson TM, Elvander-Tottie E, D'Addario C, Ekström JC, Svenningsson P, et al. The role of 5-HT (1A) receptors in learning and memory. Behav Brain Res 2008;195:54-77.  Back to cited text no. 41
Sevcik J, Nieber K, Driessen B, Illes P. Effects of the central analgesic tramadol and its main metabolite, O-desmethyltramadol, on rat locus coeruleus neurones. Br J Pharmacol 1993;110:169-76.  Back to cited text no. 42
Baghishani F, Mohammadipour A, Hosseinzadeh H, Hosseini M, Ebrahimzadeh-Bideskan A. The effects of tramadol administration on hippocampal cell apoptosis, learning and memory in adult rats and neuroprotective effects of crocin. Metab Brain Dis 2018;33:907-16.  Back to cited text no. 43
Sadeghi B, Ezzatpanah S, Haghparast A. Effects of dorsal hippocampal orexin-2 receptor antagonism on the acquisition, expression, and extinction of morphine-induced place preference in rats. Psychopharmacology (Berl) 2016;233:2329-41.  Back to cited text no. 44
Baimel C, Borgland SL. Orexin signaling in the VTA gates morphine-induced synaptic plasticity. J Neurosci 2015;35:7295-303.  Back to cited text no. 45
Prince CD, Rau AR, Yorgason JT, España RA. Hypocretin/Orexin regulation of dopamine signaling and cocaine self-administration is mediated predominantly by hypocretin receptor 1. ACS Chem Neurosci 2015;6:138-46.  Back to cited text no. 46
Sadeghi-Adl M, Sadat-Shirazi MS, Shahini F, Akbarabadi A, Khalifeh S, Borzabadi S, et al. The role of cannabinoid 1 receptor in the nucleus accumbens on tramadol induced conditioning and reinstatement. Life Sci 2020;260:118430.  Back to cited text no. 47
Piri M, Zarrindast MR, Oryan S. Effects of cannabinoidergic system of CA1 area of dorsal hippocampus on the memory of nicotine sensitized rats. Advances in Cognitive Science 2009;11:27-37.  Back to cited text no. 48
Berrendero F, Flores Á, Robledo P. When orexins meet cannabinoids: Bidirectional functional interactions. Biochem Pharmacol 2018;157:43-50.  Back to cited text no. 49
Ho YC, Lee HJ, Tung LW, Liao YY, Fu SY, Teng SF, et al. Activation of orexin 1 receptors in the periaqueductal gray of male rats leads to antinociception via retrograde endocannabinoid (2-arachidonoylglycerol)-induced disinhibition. J Neurosci 2011;31:14600-10.