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Study breakdown

Boosting endocannabinoid levels disrupted habit formation in mice

Animal StudyPreliminary evidence
The takeaway

Inhibiting the enzymes that break down endocannabinoids (FAAH and MAGL) disrupted habitual behavior formation in mice, suggesting the endocannabinoid system plays a nuanced role in how behaviors become automatic.

Addiction researchers and neuroscientists studying habit formation and the endocannabinoid system.

Both FAAH and MAGL inhibition disrupted habit formation

What the researchers found

Both FAAH inhibition (increasing anandamide) and MAGL inhibition (increasing 2-AG) disrupted habit formation during operant training in mice. This was unexpected, as previous work showed that blocking CB1 receptors also disrupted habits, suggesting that both too much and too little endocannabinoid signaling can impair habit formation.

Why it matters

Habit formation is central to substance use disorders. Understanding how endocannabinoids regulate habit formation could lead to interventions that prevent the automatic drug-seeking behaviors that drive addiction.

The numbers in context

Both FAAH and MAGL inhibitors disrupted habit formation. AM251 also disrupted habits but showed vehicle-dependent dose-response inconsistencies, raising methodological concerns about prior studies.

How the study worked

Pharmacological study using selective FAAH and MAGL inhibitors during food-reinforced operant training in mice. Habit assessed using contingency degradation. Also tested CB1 antagonist AM251 in solution vs suspension formulations.

What this study cannot tell us

Mouse model with food reward; habit formation for drugs may differ. Methodological concerns about AM251 vehicle formulations complicate interpretation of prior literature. FAAH inhibitors affect multiple lipid mediators beyond anandamide.

How to read the evidence

Well-designed behavioral pharmacology study, but mouse food-reward paradigm may not translate to human drug-seeking habits.

When this study was published

Published in 2022.

The bigger picture

The finding that augmenting endocannabinoids may prevent aberrant habit formation has potential clinical applications for preventing the compulsive behaviors seen in substance use disorders.

Questions still open

  • Could endocannabinoid-augmenting drugs prevent the transition from voluntary to compulsive drug use? Is there an optimal level of endocannabinoid signaling for healthy habit formation?

Common questions

How could this relate to addiction?
Addiction involves the transition from voluntary, goal-directed drug use to automatic, habitual drug seeking. If endocannabinoid-boosting drugs can prevent habit formation, they could potentially prevent this transition.
Isn't blocking CB1 and boosting endocannabinoids opposite approaches?
Yes, and that's the surprising finding. Both blocking CB1 (reducing signaling) and boosting endocannabinoids (increasing signaling) disrupted habits, suggesting the system needs to be in a specific balance for habits to form.

Read the original research

The effects of fatty acid amide hydrolase inhibition and monoacylglycerol lipase inhibition on habit formation in mice.

The European journal of neuroscience, 55(4), 922-938

Citation

Gianessi, Carol A; Groman, Stephanie M; Taylor, Jane R. (2022). The effects of fatty acid amide hydrolase inhibition and monoacylglycerol lipase inhibition on habit formation in mice.. The European journal of neuroscience, 55(4), 922-938. https://doi.org/10.1111/ejn.15129

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