Zebrafish (ZF; Danio rerio) larvae have become a popular in vivo model in drug metabolism
studies. Here, we investigated the metabolism of methyl 2-[1-(4-fluorobutyl)-1H-indazole-3-carboxamido]-
3,3-dimethylbutanoate (4F-MDMB-BINACA) in ZF larvae after direct administration of the cannabinoid
via microinjection, and we visualized the spatial distributions of the parent compound and its
metabolites by mass spectrometry imaging (MSI). Furthermore, using genetically modified ZF larvae,
the role of cannabinoid receptor type 1 (CB1) and type 2 (CB2) on drug metabolism was studied.
Receptor-deficient ZF mutant larvae were created using morpholino oligonucleotides (MOs), and
CB2-deficiency had a critical impact on liver development of ZF larva, leading to a significant
reduction of liver size. A similar phenotype was observed when treating wild-type ZF larvae with
4F-MDMB-BINACA. Thus, we reasoned that the cannabinoid-induced impaired liver development
might also influence its metabolic function. Studying the metabolism of two synthetic cannabinoids,
4F-MDMB-BINACA and methyl 2-(1-(5-fluoropentyl)-1H-pyrrolo[2,3-b]pyridine-3-carboxamido)-3,3-
dimethylbutanoate (70N-5F-ADB), revealed important insights into the in vivo metabolism of these
compounds and the role of cannabinoid receptor binding