The synthetic cannabinoid AKB48 stimulated reward pathways at low doses and caused dangerous effects at high doses in rats | Research

The takeaway

The synthetic cannabinoid AKB48 stimulated dopamine release in reward centers at low doses while causing hypothermia, catalepsy, heart rate depression, and sensory impairment at high doses, with all effects blocked by a CB1 antagonist.

Toxicologists, pharmacologists studying synthetic cannabinoids, and emergency physicians treating SC overdoses.

Narrow margin to toxicity

What the researchers found

AKB48 at low doses (0.25 mg/kg) preferentially stimulated dopamine release in the nucleus accumbens shell (reward center) and impaired visual reflexes at 0.3 mg/kg. Higher doses caused hypolocomotion, hypothermia, analgesia, catalepsy, and cardiorespiratory changes (bradycardia, mild bradypnea, SpO2 reduction). All effects were blocked by the CB1 antagonist AM251. Plasma AKB48 levels correlated linearly with dose and behavioral effects.

Why it matters

This is the first systematic study of AKB48 in vivo, providing a dose-response profile that explains both why users seek these drugs (low-dose dopamine stimulation) and what makes them dangerous (steep dose-response curve to dangerous effects).

The numbers in context

Low dose (0.25 mg/kg): increased dopamine in nucleus accumbens shell. 0.3 mg/kg: impaired visual reflexes. 0.5 mg/kg: impaired place preference, hypolocomotion. 3 mg/kg: hypothermia, analgesia, catalepsy, bradycardia, SpO2 reduction. All effects CB1-mediated.

How the study worked

Comprehensive pharmacological characterization in male rats: microdialysis for dopamine measurement, behavioral testing (locomotion, sensorimotor reflexes, startle/PPI, conditioned place preference), and simultaneous plasma pharmacokinetics at multiple doses.

What this study cannot tell us

Rat pharmacology may not directly translate to humans. Only male rats tested. AKB48 formulations available to users may differ from the pure compound tested. Street products often contain unknown mixtures of synthetic cannabinoids.

How to read the evidence

Rated preliminary because this is an animal study, though the comprehensive pharmacological characterization is a strength.

When this study was published

Published in 2019. AKB48 is one of many indazole synthetic cannabinoids that have appeared on the illicit market.

The bigger picture

The steep dose-response curve, from reward-seeking to cardiovascular depression, explains the narrow margin between desired effects and toxicity with synthetic cannabinoids. Users seeking a mild high are one dose miscalculation away from serious harm.

Questions still open

How do AKB48 effects compare to other synthetic cannabinoids in the same class? Is the narrow therapeutic window typical of indazole-based synthetic cannabinoids? Would CB1 antagonists have clinical utility as antidotes?

Common questions

Why is AKB48 dangerous?

The dose that produces a desirable dopamine high (0.25 mg/kg) is very close to doses causing dangerous effects like cardiac depression and catalepsy (0.5-3 mg/kg). This narrow window makes overdose easy.

How does it differ from natural cannabis?

AKB48 is a full CB1 receptor agonist, unlike THC which is a partial agonist. This means it can produce more extreme effects including complete catalepsy and significant cardiorespiratory depression.

Read the original research

Pharmacological and Behavioral Effects of the Synthetic Cannabinoid AKB48 in Rats.

Frontiers in neuroscience, 13, 1163

View on PubMed ↗Publisher’s paper ↗

Citation

Bilel, Sabrine; Tirri, Micaela; Arfè, Raffaella; Stopponi, Serena; Soverchia, Laura; Ciccocioppo, Roberto; Frisoni, Paolo; Strano-Rossi, Sabina; Miliano, Cristina; De-Giorgio, Fabio; Serpelloni, Giovanni; Fantinati, Anna; De Luca, Maria Antonietta; Neri, Margherita; Marti, Matteo. (2019). Pharmacological and Behavioral Effects of the Synthetic Cannabinoid AKB48 in Rats.. Frontiers in neuroscience, 13, 1163. https://doi.org/10.3389/fnins.2019.01163