Cannabinoid Withdrawal Is Caused by Receptor Competition, Not Inverse Agonism | Research

The takeaway

Both an inverse agonist (rimonabant) and a neutral antagonist precipitated withdrawal in cannabis-dependent mice, showing that withdrawal is caused by rapid receptor competition rather than rimonabant's inverse agonist properties.

Read this if you are interested in the neuroscience of cannabis withdrawal and potential treatment development.

Peripheral-only CB1 antagonist did not cause withdrawal; brain-penetrating ones did

What the researchers found

Researchers developed a mouse model of cannabinoid dependence using the potent, long-acting cannabinoid AM2389 and compared withdrawal precipitated by three different antagonists.

Both rimonabant (inverse agonist) and AM4113 (neutral antagonist) precipitated withdrawal signs, while AM6545 (a peripherally restricted antagonist that does not enter the brain) did not. This demonstrated two key points: withdrawal is centrally mediated (brain-based), and the inverse agonist properties of rimonabant are not responsible for withdrawal.

Withdrawal was caused by rapid competition for CB1 receptor binding, meaning the antagonist quickly displaces the agonist from the receptor. This was confirmed when reinstating AM2389 or THC reversed withdrawal symptoms.

Why it matters

Understanding that cannabinoid withdrawal is caused by receptor competition rather than inverse agonism has implications for developing cannabis addiction treatments. Neutral antagonists may be therapeutically useful without the additional risks of inverse agonists.

The numbers in context

AM2389 more potent and longer-acting than THC; both rimonabant and AM4113 precipitated withdrawal; AM6545 (peripheral only) did not; withdrawal reversed by AM2389 or THC reinstatement

How the study worked

Mouse study using AM2389 for dependence induction. Acute characterization with tetrad tests. Tolerance measured after repeated dosing. Withdrawal precipitated by three antagonists with different pharmacological properties. Reversal tested with AM2389 and THC.

What this study cannot tell us

Mouse model may not fully replicate human cannabinoid dependence. Used a very potent synthetic cannabinoid (AM2389) rather than THC for dependence induction. The psychiatric side effects of rimonabant may involve mechanisms beyond withdrawal precipitation.

How to read the evidence

Well-designed pharmacological study distinguishing mechanisms of withdrawal, but limited to a mouse model with a synthetic cannabinoid.

When this study was published

Published in 2015. Neutral CB1 antagonist development for addiction treatment continues.

The bigger picture

Rimonabant was withdrawn due to psychiatric side effects partly attributed to its inverse agonist activity. This study suggests that neutral antagonists like AM4113 could be developed as potentially safer treatments for cannabis dependence, though they would still precipitate withdrawal.

Questions still open

Would neutral CB1 antagonists have fewer psychiatric side effects than rimonabant in humans? Could gradual antagonist dosing prevent withdrawal precipitation? Is the AM2389 dependence model relevant to real-world cannabis dependence?

Common questions

What causes cannabis withdrawal?

This study showed withdrawal is caused by rapid displacement of cannabinoids from CB1 receptors in the brain. When an antagonist quickly takes the receptor away from the agonist, withdrawal symptoms occur. The process is centrally (brain) mediated.

Could this lead to a cannabis addiction treatment?

Potentially. The finding that neutral antagonists can precipitate and potentially manage withdrawal without the extra effects of inverse agonists like rimonabant suggests a safer pharmacological approach to cannabis dependence treatment.

Read the original research

Cannabinoid withdrawal in mice: inverse agonist vs neutral antagonist.

Psychopharmacology, 232(15), 2751-61

View on PubMed ↗Publisher’s paper ↗

Citation

Tai, Sherrica; Nikas, Spyros P; Shukla, Vidyanand G; Vemuri, Kiran; Makriyannis, Alexandros; Järbe, Torbjörn U C. (2015). Cannabinoid withdrawal in mice: inverse agonist vs neutral antagonist.. Psychopharmacology, 232(15), 2751-61. https://doi.org/10.1007/s00213-015-3907-0