Cannabis sativa has been associated with contradictory effects upon seizure states despite its medicinal use by numerous people with epilepsy. We have recently shown that the phytocannabinoid cannabidiol (CBD) reduces seizure severity and lethality in the well-established in vivo model of pentylenetetrazole-induced generalised seizures, suggesting that earlier, small-scale clinical trials examining CBD effects in people with epilepsy warrant renewed attention. Here, we report the effects of pure CBD (1, 10 and 100mg/kg) in two other established rodent seizure models, the acute pilocarpine model of temporal lobe seizure and the penicillin model of partial seizure. Seizure activity was video recorded and scored offline using model-specific seizure severity scales. In the pilocarpine model CBD (all doses) significantly reduced the percentage of animals experiencing the most severe seizures. In the penicillin model, CBD (≥ 10 mg/kg) significantly decreased the percentage mortality as a result of seizures; CBD (all doses) also decreased the percentage of animals experiencing the most severe tonic-clonic seizures. These results extend the anti-convulsant profile of CBD; when combined with a reported absence of psychoactive effects, this evidence strongly supports CBD as a therapeutic candidate for a diverse range of human epilepsies.

Summary Objective Epilepsy is a progressive neurological disease characterized by recurrent seizures and behavioral comorbidities. We investigated the antiseizure effect of cannabidiol ( CBD ) in a battery of acute seizure models. Additionally, we defined the disease‐modifying potential of chronic oral administration of CBD on associated comorbidities in the reduced intensity status epilepticus–spontaneous recurrent seizures ( RISE ‐ SRS ) model of temporal lobe epilepsy ( TLE ). Methods We evaluated the acute antiseizure effect of CBD in the maximal electroshock seizure, 6‐Hz psychomotor seizure, and pentylenetetrazol acute seizure tests, as well as the corneal kindling model of chronic seizures in mice following intraperitoneal administration. Median effective or behavioral toxic dose was determined in both mice and rats. Next, we tested an intravenous preparation of CBD (10 mg/kg single dose) in a rat model of pilocarpine‐induced status epilepticus. We defined the effect of chronic CBD administration (200 mg/kg orally) on spontaneous seizures, motor control, gait, and memory function in the rat RISE ‐ SRS model of TLE . Results CBD was effective in a battery of acute seizure models in both mice and rats following intraperitoneal administration. In the pilocarpine‐induced status epilepticus rat model, CBD attenuated maximum seizure severity following intravenous administration, further demonstrating CBD 's acute antiseizure efficacy in this rat model. We established that oral CBD attenuated the time‐dependent increase in seizure burden and improved TLE ‐associated motor comorbidities of epileptic rats in the RISE ‐ SRS model without affecting gait. Chronic administration of CBD after the onset of SRS ameliorated reference memory and working memory errors of epileptic animals in a spatial learning and memory task. Significance The present study illustrates that CBD is a well‐tolerated and effective antiseizure agent and illustrates a potential disease‐modifying effect of CBD on reducing both seizure burden and associated comorbidities well after the onset of symptomatic seizures in a model of TLE .

Background and Purpose Epidiolex™, a form of highly purified cannabidiol (CBD) derived from Cannabis plants, has demonstrated seizure control activity in patients with Dravet syndrome, without a fully elucidated mechanism of action. We have employed an unbiased approach to investigate this mechanism at a cellular level. Experimental Approach We use a tractable biomedical model organism, Dictyostelium, to identify a protein controlling the effect of CBD and characterize this mechanism. We then translate these results to a Dravet syndrome mouse model and an acute in vitro seizure model. Key Results CBD activity is partially dependent upon the mitochondrial glycine cleavage system component, GcvH1 in Dictyostelium, orthologous to the human glycine cleavage system component H protein, which is functionally linked to folate one‐carbon metabolism (FOCM). Analysis of FOCM components identified a mechanism for CBD in directly inhibiting methionine synthesis. Analysis of brain tissue from a Dravet syndrome mouse model also showed drastically altered levels of one‐carbon components including methionine, and an in vitro rat seizure model showed an elevated level of methionine that is attenuated following CBD treatment. Conclusions and Implications Our results suggest a novel mechanism for CBD in the regulating methionine levels and identify altered one‐carbon metabolism in Dravet syndrome and seizure activity.