Rats bred for depression-like behavior had lower 2-AG levels in left-brain regions and altered endocannabinoid system components, with changes varying by hemisphere.
Neuroscientists, depression researchers, and anyone interested in endocannabinoid system involvement in mood disorders.
Hemisphere-specific deficits
What the researchers found
2-AG was lower in the left hippocampus and left prefrontal cortex of depression-prone FSL rats compared to controls. AEA was higher in the right hippocampus. CB1 receptor and FAAH protein levels were decreased in the left hippocampus, while mRNA for multiple eCB components was decreased in the right prefrontal cortex.
Why it matters
If depression involves hemisphere-specific endocannabinoid deficits, treatments targeting the eCB system might need to account for lateralized brain function, a nuance most current approaches overlook.
The numbers in context
2-AG was significantly lower in left hippocampus and left prefrontal cortex of FSL rats. AEA was elevated in right hippocampus. Plasma AEA was increased and 2-AG decreased in FSL rats.
How the study worked
Compared endocannabinoid levels (LC/MRM), receptor expression (qPCR), and protein levels (Western blot) in left and right prefrontal cortex and hippocampus of Flinders Sensitive Line (depression model) vs. Flinders Resistant Line rats.
What this study cannot tell us
Animal model using inbred rat strains, which may not fully represent human depression. Small sample sizes typical of such studies. Hemisphere-specific findings need replication.
How to read the evidence
Preliminary: animal model with no direct human data.
When this study was published
Published in 2019.
The bigger picture
The endocannabinoid system is increasingly implicated in depression, but this study adds an unexpected layer: the changes are not uniform across the brain. Left-right differences may help explain why depression manifests differently across individuals.
Questions still open
- Do humans with depression show similar hemisphere-specific endocannabinoid differences? Could lateralized eCB deficits explain why some people respond to cannabinoid treatments and others do not?
Common questions
What is the endocannabinoid system's role in depression?
Why do left and right brain differences matter?
Read the original research
Hemisphere-dependent endocannabinoid system activity in prefrontal cortex and hippocampus of the Flinders Sensitive Line rodent model of depression.
Neurochemistry international, 125, 7-15
Citation
Kirkedal, C; Elfving, B; Müller, H K; Moreira, F A; Bindila, L; Lutz, B; Wegener, G; Liebenberg, N. (2019). Hemisphere-dependent endocannabinoid system activity in prefrontal cortex and hippocampus of the Flinders Sensitive Line rodent model of depression.. Neurochemistry international, 125, 7-15. https://doi.org/10.1016/j.neuint.2019.01.023
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