Developmental toxicity and gene expression alterations induced by the synthetic cannabinoid CUMYL-4CN-BINACA in zebrafish embryos

Synthetic cannabinoids like CUMYL-4CN-BINACA are emerging psychoactive substances with largely unknown developmental toxicity. Given the growing concern about prenatal and early-life exposure, this study assessed its impact on zebrafish embryos, focusing on morphological development, larval behavior, and gene expression. Embryos were exposed to concentrations of 1.25–40.0 mg/L during short-term (3–24 hpf) and long-term (3–120 hpf) windows. Key developmental endpoints, including survival, heartbeat, hatching, and locomotor activity, were evaluated. Molecular analyses were performed using qPCR to assess the expression of 19 genes related to apoptosis, behavior, and neurotransmission. Short-term exposure did not produce significant morphological changes, while long-term exposure resulted in concentration-dependent teratogenic effects such as pericardial and yolk sac edema, axial deformities, and hypoactivity. The LC50 and EC50 at 120 hpf were calculated as 16.624 mg/L and 9.083 mg/L, respectively. Gene expression analysis revealed significant alterations in behavioral genes (gnrh3, gnrhr3, kiss2), apoptotic markers (casp3a, casp8, ifng1, tp53), and the DNA repair gene rad51. Neurotransmission-related genes in dopaminergic (dat, drd1, drd3), serotonergic (5ht1aa, 5ht1a, 5ht1b, 5ht2c), and GABAergic (gabra1, gat1, abat, gad1b) systems were also dysregulated. These findings highlight the developmental and neurotoxic potential of CUMYL-4CN-BINACA, underlining the need for further toxicological risk assessments in early vertebrate models.