1. Filipowicz W BS, Sonenber N. Mechanisms of post-transcriptional regulation by microRNAs: are the answers in sight? Nat Rev Genet 2008, 9:13.

2. Kalivas PW, Volkow ND. The neural basis of addiction: A pathology of motivation and choice. American Journal of Psychiatry 2005, 162: 1403–1413.

3. [3] Koob GF, Volkow ND. Neurocircuitry of addiction. Neuropsychopharmacology 2010, 35: 217–238.

4. Aldworth J AK, Bishop E. Results from the 2006 National Survey on Drug Use and Health: national findings. 2007.

5. Niciu MJ, Kelmendi B, Sanacora G. Overview of glutamatergic neurotransmission in the nervous system. Pharmacol Biochem Behav 2012, 100: 656–664.

6. Kessels HW, Malinow R. Synaptic AMPA receptor plasticity and behavior. Neuron 2009, 61: 340–350.

7. Cunha-Oliveira T, Rego AC, Oliveira CR. Cellular and molecular mechanisms involved in the neurotoxicity of opioid and psychostimulant drugs. Brain Res Rev 2008, 58: 192–208.

8. Koob GF. Neuroadaptive mechanisms of addiction: studies on the extended amygdala. Eur Neuropsychopharmacol 2003, 13: 442–452.

9. Enrico P, Mura MA, Esposito G, Serra P, Migheli R, De Natale G, et al. Effect of naloxone on morphine-induced changes in striatal dopamine metabolism and glutamate, ascorbic acid and uric acid release in freely moving rats. Brain Res 1998, 797: 94–102.

10. Siggins GR, Martin G, Roberto M, Nie Z, Madamba S, De Lecea L. Glutamatergic transmission in opiate and alcohol dependence. Ann N Y Acad Sci 2003, 1003: 196–211.

11. Glass MJ, Kruzich PJ, Kreek MJ, Pickel VM. Decreased plasma membrane targeting of NMDA-NR1 receptor subunit in dendrites of medial nucleus tractus solitarius neurons in rats self-administering morphine. Synapse 2004, 53: 191–201.

12. Yu H, Chen ZY. The role of BDNF in depression on the basis of its location in the neural circuitry. Acta Pharmacol Sin 2011, 32: 3–11.

13. Williams JT, Christie MJ, Manzoni O. Cellular and synaptic adaptations mediating opioid dependence. Physiol Rev 2001, 81: 299–343.

14. Berke JD, Eichenbaum HB. Drug addiction and the hippocampus. Science 2001, 294: 1235.

15. Farahmandfar M, Karimian SM, Zarrindast MR, Kadivar M, Afrouzi H, Naghdi N. Morphine sensitization increases the extracellular level of glutamate in CA1 of rat hippocampus via mu-opioid receptor. Neurosci Lett 2011, 494: 130–134.

16. Guo M, Xu NJ, Li YT, Yang JY, Wu CF, Pei G. Morphine modulates glutamate release in the hippocampal CA1 area in mice. Neurosci Lett 2005, 381: 12–15.

17. Tzschentke TM, Schmidt WJ. Glutamatergic mechanisms in addiction. Mol Psychiatry 2003, 8: 373–382.

18. Sepehrizadeh Z, Sahebgharani M, Ahmadi S, Shapourabadi MB, Bozchlou SH, Zarrindast MR. Morphine-induced behavioral sensitization increased the mRNA expression of NMDA receptor subunits in the rat amygdala. Pharmacology 2008, 81: 333–343.

19. Sepehrizadeh Z, Bahrololoumi Shapourabadi M, Ahmadi S, Hashemi Bozchlou S, Zarrindast MR, Sahebgharani M. Decreased AMPA GluR2, but not GluR3, mRNA expression in rat amygdala and dorsal hippocampus following morphine-induced behavioural sensitization. Clin Exp Pharmacol Physiol 2008, 35: 1321–1330.

20. Reis DJ, Regunathan S. Is agmatine a novel neurotransmitter in brain? Trends Pharmacol Sci 2000, 21: 187–193.

21. Piletz JE, Aricioglu F, Cheng JT, Fairbanks CA, Gilad VH, Haenisch B, et al. Agmatine: clinical applications after 100 years in translation. Drug Discov Today 2013, 18: 880–893.

22. Uzbay TI. The pharmacological importance of agmatine in the brain. Neurosci Biobehav Rev 2012, 36: 502–519.

23. Wei XL, Su RB, Lu XQ, Liu Y, Yu SZ, Yuan BL, et al. Inhibition by agmatine on morphine-induced conditioned place preference in rats. Eur J Pharmacol 2005, 515: 99–106.

24. Li J, Li X, Pei G, Qin BY. Analgesic effect of agmatine and its enhancement on morphine analgesia in mice and rats. Zhongguo Yao Li Xue Bao 1999, 20: 81–85.

25. Li J, Li X, Pei G, Qin BY. Effects of agmatine on tolerance to and substance dependence on morphine in mice. Zhongguo Yao Li Xue Bao 1999, 20: 232–238.

26. Aricioglu-Kartal F, Uzbay IT. Inhibitory effect of agmatine on naloxone-precipitated abstinence syndrome in morphine dependent rats. Life Sci 1997, 61: 1775–1781.

27. Kolesnikov Y, Jain S, Pasternak GW. Modulation of opioid analgesia by agmatine. Eur J Pharmacol 1996, 296: 17–22.

28. Wang XF, Wu N, Su RB, Lu XQ, Liu Y, Li J. Agmatine modulates neuroadaptations of glutamate transmission in the nucleus accumbens of repeated morphine-treated rats. Eur J Pharmacol 2011, 650: 200–205.

29. Wen ZH, Chang YC, Cherng CH, Wang JJ, Tao PL, Wong CS. Increasing of intrathecal CSF excitatory amino acids concentration following morphine challenge in morphine-tolerant rats. Brain Res 2004, 995: 253–259.

30. Ortiz J, Fitzgerald LW, Charlton M, Lane S, Trevisan L, Guitart X, et al. Biochemical actions of chronic ethanol exposure in the mesolimbic dopamine system. Synapse 1995, 21: 289–298.

31. Ullensvang K, Lehre KP, Storm-Mathisen J, Danbolt NC. Differential developmental expression of the two rat brain glutamate transporter proteins GLAST and GLT. Eur J Neurosci 1997, 9: 1646–1655.

32. Kalivas PW, Lalumiere RT, Knackstedt L, Shen H. Glutamate transmission in addiction. Neuropharmacology 2009, 56 Suppl 1: 169–173.

33. Wei XL, Su RB, Wu N, Lu XQ, Zheng JQ, Li J. Agmatine inhibits morphine-induced locomotion sensitization and morphine-induced changes in striatal dopamine and metabolites in rats. Eur Neuropsychopharmacol 2007, 17: 790–799.

34. Reissner KJ, Kalivas PW. Using glutamate homeostasis as a target for treating addictive disorders. Behav Pharmacol 2010, 21: 514–522.

35. Feng Y, LeBlanc MH, Regunathan S. Agmatine reduces extracellular glutamate during pentylenetetrazole-induced seizures in rat brain: a potential mechanism for the anticonvulsive effects. Neurosci Lett 2005, 390: 129–133.

36. Kalivas PW. The glutamate homeostasis hypothesis of addiction. Nat Rev Neurosci 2009, 10: 561–572.

37. Singewald N, Philippu A. Release of neurotransmitters in the locus coeruleus. Prog Neurobiol 1998, 56: 237–267.

38. Wang G, Gorbatyuk OS, Dayanithi G, Ouyang W, Wang J, Milner TA, et al. Evidence for endogenous agmatine in hypothalamo-neurohypophysial tract and its modulation on vasopressin release and Ca2 + channels. Brain Res 2002, 932: 25–36.

39. Weng XC, Gai XD, Zheng JQ, Li J. Agmatine blocked voltage-gated calcium channel in cultured rat hippocampal neurons. Acta Pharmacol Sin 2003, 24: 746–750.

40. Xu NJ, Bao L, Fan HP, Bao GB, Pu L, Lu YJ, et al. Morphine withdrawal increases glutamate uptake and surface expression of glutamate transporter GLT1 at hippocampal synapses. J Neurosci 2003, 23: 4775–4784.

41. Wilson NR, Kang J, Hueske EV, Leung T, Varoqui H, Murnick JG, et al. Presynaptic regulation of quantal size by the vesicular glutamate transporter VGLUT1. J Neurosci 2005, 25: 6221–6234.

42. Martin G, Guadano-Ferraz A, Morte B, Ahmed S, Koob GF, De Lecea L, et al. Chronic morphine treatment alters N-methyl-D-aspartate receptors in freshly isolated neurons from nucleus accumbens. J Pharmacol Exp Ther 2004, 311: 265–273.

43. Cull-Candy S, Brickley S, Farrant M. NMDA receptor subunits: diversity, development and disease. Curr Opin Neurobiol 2001, 11: 327–335.

44. Narita M, Aoki T, Suzuki T. Molecular evidence for the involvement of NR2B subunit containing N-methyl-D-aspartate receptors in the development of morphine-induced place preference. Neuroscience 2000, 101: 601–606.

45. Kao JH, Huang EY, Tao PL. NR2B subunit of NMDA receptor at nucleus accumbens is involved in morphine rewarding effect by siRNA study. Drug Alcohol Depend 2011, 118: 366–374.

46. Johansson T, Elfverson M, Zhou Q, Nyberg F. Allosteric modulation of the NMDA receptor by neurosteroids in rat brain and the impact of long term morphine administration. Biochem Biophys Res Commun 2010, 401: 504–508.

47. Turchan J, Maj M, Przewlocka B. The effect of drugs of abuse on NMDAR1 receptor expression in the rat limbic system. Drug Alcohol Depend 2003, 72: 193–196.