Phenotype-based screening of synthetic cannabinoids in a Dravet Syndrome zebrafish model

Abstract

Dravet syndrome (DS) is a catastrophic epilepsy of childhood, characterized by cognitive impairment, severe seizures and increased risk for sudden unexplained death in epilepsy (SUDEP). Although refractory to conventional antiepileptic drugs, emerging preclinical and clinical evidence suggests that modulation of the endocanniboid system could be therapeutic in these patients. Here we used a validated zebrafish model of DS, scn1lab homozygous mutants, to screen a commercially available library containing 370 synthetic cannabinoid (SC) compounds for compounds effective in reducing spontaneous seizures. Primary phenotype-based screening was performed using a locomotion-based assay in 96-well plates, and a secondary local field potential recording assay was then used to confirm suppression of electrographic epileptiform events. Identified SCs with anti-seizure activity, in both assays, included five SCs structurally classified as indole-based cannabinoids: JWH 018 N-(5-chloropentyl) analog, JWH 018 N-(2-methylbutyl) isomer, 5-fluoro PB-22 5-hydroxyisoquinoline isomer, 5-fluoro ADBICA, and AB-FUBINACA 3-fluorobenzyl isomer. Our approach demonstrates that two-stage phenotype-based screening in a zebrafish model of DS successfully identifies synthetic cannabinoids with anti-seizure activity, and supports further investigation of SCs for refractory epilepsies.