Aquatic toxicity of synthetic cannabinoid: multisystem impacts of 5F-ADB on neurodevelopment in <i>Daphnia magna</i>

As a synthetic cannabinoid classified as an illicit drug in China and most European countries, methyl 2-{[1-(5-fluoropentyl)-1H-indazole-3-carbonyl]amino}-3,3-dimethylbutanoate (5F-ADB) poses emerging environmental risks due to potential aquatic contamination through wastewater discharge. This study systematically investigated the multilevel toxicity of 5F-ADB in Daphnia magna (D. magna) over a 21-day exposure. In general, 5F-ADB caused significant developmental inhibition in body length and weight (p < 0.05 and p < 0.01), and it caused developmental delays in D. magna. The heart rate of exposed D. magna decreased, but their respiratory rate increased. Methyl 2-{[1-(5-fluoropentyl)-1H-indazole-3-carbonyl]amino}-3,3-dimethylbutanoate has a low promotion and high inhibition effect on daphnia reproduction. Meanwhile, 5F-ADB has a stimulating effect on the swimming behavior of D. magna, showing a significant activity stimulation. The oxidative stress system of exposed D. magna was significantly disrupted by 5F-ADB, and 5F-ADB also altered the neurotransmitter levels of daphnia. The inhibition of the serotonergic and noradrenergic systems may be the potential mechanism for excited swimming behavior of exposed D. magna. These results demonstrate that 5F-ADB exerts multidimensional toxicity in zooplankton, highlighting the urgent need for ecological risk assessment of novel psychoactive substances in aquatic environments.