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41.• Graham BM, Milad MR. Inhibition of estradiol synthesis impairs fear extinction in male rats. Learn Mem. 2014;21:347–50. This study demonstrated that blockade of estradiol in males impaired extinction recall. This suggests that estradiol is an important regulator of fear not only in females, but also in males.

42.• Graham BM, Milad MR. Blockade of estrogen by hormonal contraceptives impairs fear extinction in female rats and women. Biol Psychiatry. 2013;73:371–8. This study demonstrates how hormonal contraceptive use induces a deficit in extinction recall. It also demonstrates how estradiol administration to naturally cycling women can increase extinction recall.

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56.• Rabinak CA, Angstadt M, Lyons M, Mori S, Milad MR, Liberzon I, et al. Cannabinoid modulation of prefrontal-limbic activation during fear extinction learning and recall in humans. Neurobiol Learn Mem. 2014;113:125–34. Important study demonstrating how THC can promote activation of the vmPFC and hippocampus during extinction recall.

57. Neumeister A, Seidel J, Ragen BJ, Pietrzak RH. Translational evidence for a role of endocannabinoids in the etiology and treatment of posttraumatic stress disorder. Psychoneuroendocrinology. 2015;51:577–84.

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64.• Telch MJ, Bruchey AK, Rosenfield D, Cobb AR, Smits J, Pahl S, et al. Effects of post-session administration of methylene blue on fear extinction and contextual memory in adults with claustrophobia. Am J Psychiatry. 2014;171:1091–8. First clinical report suggesting that methylene blue could be a good adjunct to exposure therapy. The paper also points to the importance of administering MB only following successful sessions.

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66. Levenson JM, O’Riordan KJ, Brown KD, Trinh MA, Molfese DL, Sweatt JD. Regulation of histone acetylation during memory formation in the hippocampus. J Biol Chem. 2004;279:40545–59.

67.• Gräff J, Tsai L-H. The potential of HDAC inhibitors as cognitive enhancers. Annu Rev Pharmacol Toxicol. 2013;53:311–30. Very good review on HDAC inhibitors, their actions, their potential use as cognitive enhancers as well as some limitations that need to be taken into account.

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