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Role of endocannabinoids in the hippocampus and amygdala in emotional memory and plasticity

Neuropsychopharmacologyvolume 43pages20172027 (2018) | Download Citation


Posttraumatic stress disorder (PTSD) is characterized by the reexperiencing of a traumatic event and is associated with slower extinction of fear responses. Impaired extinction of fearful associations to trauma-related cues may interfere with treatment response, and extinction deficits may be premorbid risk factors for the development of PTSD. We examined the effects of exposure to a severe footshock followed by situational reminders (SRs) on extinction, plasticity, and endocannabinoid (eCB) content and activity in the hippocampal CA1 area and basolateral amygdala (BLA). We also examined whether enhancing eCB signaling before extinction, using the fatty acid amide hydrolase (FAAH) inhibitor URB597, could prevent the shock/SRs-induced effects on fear response and plasticity. URB597 administered systemically (0.3 mg/kg) or locally into the CA1 or BLA (0.1 µg/side) prior to extinction decreased fear retrieval and this effect persisted throughout extinction training and did not recuperate during spontaneous recovery. A low dose of the CB1 receptor antagonist AM251 (0.3 mg/kg i.p. or 0.01 µg/0.5 µl intra-CA1 or intra-BLA) blocked these effects suggesting that the effects of URB597 were CB1 receptor-dependent. Exposure to shock and reminders induced behavioral metaplasticity with opposite effects on long-term potentiation (LTP) in the hippocampus (impairment) and the BLA (enhancement). URB597 was found to prevent the opposite shock/SR-induced metaplasticity in hippocampal and BLA-LTP. Exposure to shock and reminders might cause variation in endogenous cannabinoid levels that could affect fear-circuit function. Indeed, exposure to shock and SRs affected eCB content: increased 2-arachidonoyl-glycerol (2-AG) and N-arachidonylethanolamine (AEA) levels in the CA1, decreased serum and BLA AEA levels while shock exposure increased FAAH activity in the CA1 and BLA. FAAH inhibition before extinction abolished fear and modulated LTP in the hippocampus and amygdala, brain regions pertinent to emotional memory. The findings suggest that targeting the eCB system before extinction may be beneficial in fear memory attenuation and these effects may involve metaplasticity in the CA1 and BLA.

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This research was supported by The Binational Science Foundation (BSF) [Grant no. 2011/256 to I.A. and C.J.H. (URL:] and by the Research and Education Component of the Advancing a Healthier Wisconsin Endowment at the Medical College of Wisconsin.

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Author notes

  1. These authors contributed equally: Tomer Mizrachi Zer-Aviv, Nachshon Korem, Amir Segev.


  1. Department of Psychology, University of Haifa, Haifa, 3498838, Israel

    • Amir Segev
    • , Nachshon Korem
    • , Tomer Mizrachi Zer-Aviv
    • , Hila Abush
    •  & Irit Akirav
  2. Department of Pharmacology and Toxicology, Neuroscience Research Center, Medical College of Wisconsin, Milwaukee, 53226, USA

    • Rachel Lange
    • , Garrett Sauber
    •  & Cecilia J. Hillard


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Correspondence to Amir Segev.

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