Synthetic cannabinoids worsened alcohol-related motor impairment in mice by reducing brain glutamate | Research

The takeaway

In mice, combining synthetic cannabinoids (JWH-018 or AB-CHMINACA) with alcohol produced greater motor impairment than either substance alone, through a mechanism involving reduced glutamate signaling in the cerebellum.

Toxicologists, driving safety researchers, and those interested in synthetic cannabinoid pharmacology.

Synthetic cannabinoids + alcohol = greater motor impairment via CB1

What the researchers found

Synthetic cannabinoids enhanced ethanol-induced motor impairment on a rotarod test. This effect was blocked by a CB1 receptor antagonist but not a CB2 antagonist. The combination reduced extracellular glutamate levels in the cerebellum more than alcohol alone.

Why it matters

Synthetic cannabinoids and alcohol are frequently used together, and this study identifies a specific brain mechanism (reduced cerebellar glutamate) that explains why the combination causes worse motor impairment than either substance alone.

The numbers in context

Ethanol dose: 2 g/kg. Two synthetic cannabinoids tested: JWH-018 and AB-CHMINACA. Effects blocked by CB1 antagonist AM251 but not CB2 antagonist AM630.

How the study worked

Mouse study testing motor coordination on an accelerating rotarod after administering ethanol (2 g/kg) alone or combined with JWH-018 or AB-CHMINACA. Microdialysis measured cerebellar glutamate levels. Microelectrode arrays assessed neuronal network activity in cerebellar cultures.

What this study cannot tell us

Animal study using injected synthetic cannabinoids, which may not replicate human exposure patterns. Only two synthetic cannabinoids were tested among hundreds that exist. The specific glutamate mechanism may not fully explain real-world impairment.

How to read the evidence

Preliminary: animal study establishing mechanism, not yet confirmed in humans.

When this study was published

Published in 2020 in Toxicology and Applied Pharmacology.

The bigger picture

The finding has direct relevance to driving safety and injury risk, as many synthetic cannabinoid users also drink alcohol, and the combination produces motor impairments greater than either substance alone.

Questions still open

Do natural cannabis and alcohol show the same synergistic motor impairment mechanism? Could this cerebellar glutamate pathway be a target for reducing combined impairment?

Common questions

Why is this combination dangerous?

Both synthetic cannabinoids and alcohol impair motor coordination individually. This study shows the combination has a synergistic effect, reducing cerebellar glutamate more than either substance alone, leading to even worse motor impairment.

Does natural cannabis interact with alcohol the same way?

This study only tested synthetic cannabinoids. While natural THC and alcohol are also known to impair motor function together, the specific mechanism may differ because synthetic cannabinoids often have higher potency at CB1 receptors.

Read the original research

Synthetic cannabinoids enhanced ethanol-induced motor impairments through reduction of central glutamate neurotransmission.

Toxicology and applied pharmacology, 408, 115283

View on PubMed ↗Publisher’s paper ↗

Citation

Funada, Masahiko; Takebayashi-Ohsawa, Mika; Tomiyama, Ken-Ich. (2020). Synthetic cannabinoids enhanced ethanol-induced motor impairments through reduction of central glutamate neurotransmission.. Toxicology and applied pharmacology, 408, 115283. https://doi.org/10.1016/j.taap.2020.115283