In rats with extinction-resistant fear (modeling PTSD), a CB1 agonist reduced anxiety-like behavior, but neither it nor an endocannabinoid-boosting drug altered the expression of conditioned fear memories.
PTSD researchers, neuroscientists studying fear circuits, and clinicians interested in cannabinoid-based anxiety treatments.
CB1 agonist reduced anxiety but did not alter fear recall
What the researchers found
Acute WIN55,212-2 (CB1 agonist) reduced anxiety in "weak extinction" rats but did not affect fear recall. The FAAH inhibitor URB597 did not reduce anxiety or fear acutely. The CB1 inverse agonist AM251 increased anxiety in normal-extinction rats. Chronic administration of neither URB597 nor AM251 altered fear or anxiety, and did not change FAAH or CB1 expression.
Why it matters
PTSD involves both anxiety and persistent fear memories. This study suggests the endocannabinoid system may help with PTSD-related anxiety but may not be sufficient to eliminate extinction-resistant fear memories.
The numbers in context
25-30% of rats showed weak extinction (modeling PTSD). WIN55,212-2 reduced anxiety in WE rats. AM251 increased anxiety in SE rats. No drug condition altered freezing during fear recall.
How the study worked
Rats underwent fear conditioning and were segregated into weak extinction (WE, modeling PTSD) and strong extinction (SE) groups. Acute and chronic endocannabinoid-modulating drugs were tested on fear recall and novelty-suppressed feeding (anxiety measure).
What this study cannot tell us
Animal model may not fully capture human PTSD complexity. Systemic drug administration does not target specific brain regions. Only one dose of each drug was tested. Fear recall was measured by freezing, which may not capture all aspects of fear response.
How to read the evidence
Controlled preclinical study with relevant behavioral paradigm, but systemic drug delivery and single-dose testing limit conclusions.
When this study was published
2020 animal study. Helps clarify which PTSD symptoms might respond to endocannabinoid modulation.
The bigger picture
The distinction between anxiety and fear memory is important for PTSD treatment. Endocannabinoid-based therapies might address generalized anxiety in PTSD without necessarily helping with the core trauma memories.
Questions still open
- Would targeted brain-region delivery of endocannabinoid drugs be more effective for fear extinction? Could combining endocannabinoid therapy with exposure therapy improve outcomes? Do different cannabinoid compounds have different effects on fear vs. anxiety?
Common questions
What are weak extinction rats?
Why did the CB1 agonist help anxiety but not fear?
Read the original research
Endocannabinoid modulating drugs improve anxiety but not the expression of conditioned fear in a rodent model of post-traumatic stress disorder.
Neuropharmacology, 166, 107965
Citation
Vimalanathan, Akshayan; Gidyk, Darryl C; Diwan, Mustansir; Gouveia, Flavia V; Lipsman, Nir; Giacobbe, Peter; Nobrega, José N; Hamani, Clement. (2020). Endocannabinoid modulating drugs improve anxiety but not the expression of conditioned fear in a rodent model of post-traumatic stress disorder.. Neuropharmacology, 166, 107965. https://doi.org/10.1016/j.neuropharm.2020.107965
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