Animal models of epilepsy are often used to test the effects of new drug treatments on seizure occurrence. In this study, a research team led by EpLink co-director Dr. McIntyre Burnham examined the effects of cannabis extracts on seizure frequency in a model of focal impaired awareness seizures (FIASs). FIASs, previously known as complex partial seizures, are one of the most common seizure types and are very difficult to treat since seizures often do not respond to standard antiseizure medications. Previous studies have found that the cannabis extract cannabidiol (CBD) can reduce seizure frequency in people with certain epilepsy syndromes when used along with antiseizure medication.
The researchers were interested in whether CBD or Δ9-tetrahydrocannabinol (THC), another cannabis extract, could potentially be used to treat FIASs as well. In this study, the research team used a technique known as kindling to mimic the development of FIASs. In rat models, kindling occurs when repeated electrical stimulation is delivered to a particular brain region to make it more likely for a seizure to occur. The researchers performed this technique on the amygdala, in an area of the brain known as the temporal lobe, which is often where seizures begin. Once kindling was complete, the researchers injected the rats with either THC alone, CBD alone or a combination of CBD and THC. Afterwards, they examined the effects on seizure frequency using electroencephalography, or EEG.
The EEG recordings showed that CBD alone and THC alone were able to reduce seizures to some degree, but the combination of CBD and THC was much more effective at suppressing seizures. Importantly, no toxic side effects were seen in any of the animals. There was no clear link between the dose given and the amount of seizure suppression. For example, in rats given a combination of CBD and THC, the greatest reduction in seizures occurred at the lowest dose. This suggests that there might be a difference between responders and non-responders, meaning that cannabis extracts may be more beneficial in some patients than others. More research is needed to understand why the combination of CBD and THC may be more effective than either extract alone, and which patients with FIASs may be most likely to benefit from this type of treatment.