Endocannabinoid 2-AG in the brain's pain-processing region modulated fear-driven pain suppression via CB2 receptors
Increasing 2-AG levels in the anterior cingulate cortex attenuated fear-conditioned analgesia in rats, an effect blocked by a CB2 receptor antagonist but not a CB1 antagonist.
Quick Facts
What This Study Found
MGL inhibition (increasing 2-AG) in the ACC attenuated fear-conditioned analgesia. This effect was blocked by the CB2 antagonist AM630 but not the CB1 antagonist AM251. The CB2 antagonist alone reduced pain behavior in non-fear-conditioned rats. Both CB1 and CB2 receptor mRNA were confirmed in the ACC.
Key Numbers
MJN110 increased 2-AG levels in ACC and attenuated FCA. AM630 (CB2 antagonist) blocked MJN110's effect. AM251 (CB1 antagonist) did not alter MJN110's effect. CB1 and CB2 mRNA confirmed in ACC.
How They Did This
Male rats underwent fear conditioning (arena paired with footshock) followed by formalin-evoked pain testing. Microinjection of MGL inhibitor MJN110, CB2 antagonist AM630, or CB1 antagonist AM251 into the anterior cingulate cortex. 2-AG levels confirmed via mass spectrometry.
Why This Research Matters
Understanding how the brain's own pain-suppression systems work through the endocannabinoid system could reveal new therapeutic targets for pain and fear-related disorders.
The Bigger Picture
The finding that CB2 (not CB1) receptors mediate this effect in a cortical brain region is surprising, as CB2 was traditionally considered a peripheral immune receptor. This expands understanding of CB2's role in the brain.
What This Study Doesn't Tell Us
Animal model; male rats only; fear-conditioned analgesia is one specific form of endogenous pain suppression; pharmacological specificity of tools used.
Questions This Raises
- ?Could CB2-targeted drugs modulate pain processing in humans?
- ?What role does 2-AG play in other cortical regions involved in pain?
Trust & Context
- Key Stat:
- CB2 (not CB1) receptors mediated the 2-AG effect on fear-conditioned analgesia in the cortex
- Evidence Grade:
- Single animal study with clean pharmacological dissection of receptor subtypes.
- Study Age:
- Published in 2020.
- Original Title:
- Attenuation of fear-conditioned analgesia in rats by monoacylglycerol lipase inhibition in the anterior cingulate cortex: Potential role for CB2 receptors.
- Published In:
- British journal of pharmacology, 177(10), 2240-2255 (2020)
- Authors:
- Corcoran, Louise(2), Mattimoe, Darragh(2), Roche, Michelle(4), Finn, David P
- Database ID:
- RTHC-02478
Evidence Hierarchy
Tests effects in animals (usually mice or rats), not humans.
What do these levels mean? →Frequently Asked Questions
What is fear-conditioned analgesia?
When an animal or person is in a fearful situation, the brain can suppress pain signals. This natural pain reduction, called fear-conditioned analgesia, is thought to be an adaptive response that allows action during threatening situations.
Why is the CB2 receptor finding surprising?
CB2 receptors were traditionally considered peripheral immune receptors. Finding that CB2 mediates endocannabinoid effects on pain processing in a cortical brain region challenges this view and suggests brain CB2 receptors play a more important role than previously thought.
Read More on RethinkTHC
- CBD-oil-quality-guide
- anxiety-medication-after-quitting-weed
- cannabis-chemotherapy-nausea
- cannabis-chronic-pain-research
- cannabis-epilepsy-CBD-Epidiolex
- cbd-anxiety-research-evidence
- cbd-for-weed-withdrawal
- cbd-vs-thc-difference
- medical-benefits-of-cannabis
- quitting-weed-before-surgery
- quitting-weed-medication-interactions
- quitting-weed-pregnancy
- quitting-weed-pregnant
- seniors-older-adults-cannabis-risks-medications
- weed-breastfeeding-THC-breast-milk
Cite This Study
https://rethinkthc.com/research/RTHC-02478APA
Corcoran, Louise; Mattimoe, Darragh; Roche, Michelle; Finn, David P. (2020). Attenuation of fear-conditioned analgesia in rats by monoacylglycerol lipase inhibition in the anterior cingulate cortex: Potential role for CB2 receptors.. British journal of pharmacology, 177(10), 2240-2255. https://doi.org/10.1111/bph.14976
MLA
Corcoran, Louise, et al. "Attenuation of fear-conditioned analgesia in rats by monoacylglycerol lipase inhibition in the anterior cingulate cortex: Potential role for CB2 receptors.." British journal of pharmacology, 2020. https://doi.org/10.1111/bph.14976
RethinkTHC
RethinkTHC Research Database. "Attenuation of fear-conditioned analgesia in rats by monoacy..." RTHC-02478. Retrieved from https://rethinkthc.com/research/corcoran-2020-attenuation-of-fearconditioned-analgesia
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.