CBD can be combined with additional cannabinoids for optimal seizure reduction and requires GPR55 for its anticonvulsant effects

Background Cannabis has demonstrated anticonvulsant properties, and cannabis-based medicines are approved to treat pediatric patients with severe pediatric epilepsies that are particularly refractive to approved anti-epileptic drugs (AEDs). About thirty percent of epileptic patients do not have satisfactory seizure management with AEDs and could potentially benefit from cannabis-based intervention. Here we report the use of single and combined cannabinoids to treat Pentylenetetrazol (PTZ) induced convulsions in a zebrafish model, their effect on gene expression, and a simple assay for assessing their uptake in zebrafish tissues. These data provide novel insights as to the potential of treating epilepsy with cannabinoids. Methods Zebrafish larvae were treated with cannabinoids and their seizures measured through an optimized behaviour tracking method. Cannabinoid uptake was measured with a novel HPLC-UV method. Gene expression changes were assessed using quantitative PCR (qPCR), and chemical inhibitors of potential cannabinoid receptors were used to block activity. Results Treatment with cannabinol (CBN), cannabichromene (CBC) and cannabigerol (CBG) decreased seizure intensity at lower doses than CBD when accounting for the amount of cannabinoid recovered from exposed larvae. Δ9-tetrahydrocannabinol (Δ9-THC), Δ8-tetrahydrocannabinol (Δ8-THC) were effective at higher doses. Synergistic effects were observed between CBD and other cannabinoids such as Δ9-THC, Δ8-THC, and CBG. The reduction of PTZ induced seizures via CBD is partially mediated by the G-protein coupled receptor GPR55, as pharmacological inhibition of the receptor reduced the therapeutic action of CBD. Changes in expression of endocannabinoid system ( napepld, gde1, faah, ptgs2a ) and neural ( fosab, pyya ) genes in response to phytocannabinoid treatment were observed and highlight novel mechanisms of phytocannabinoid action. Conclusions CBD can be combined with additional cannabinoids for optimal reduction of seizure activity and requires the activity of GPR55. Changes in fosab regulation of gene expression and endocannabinoid signalling may influence the anticonvulsant effects of cannabis, however further investigation is required. ### Competing Interest Statement The authors have declared no competing interest.