Marijuana-like brain substance calms seizures but increases aftereffects, study finds
Release of the brain’s equivalent of THC, marijuana’s active component, reduces seizure activity but leads to post-seizure oxygen deprivation in the brain, Stanford scientists and their collaborators have shown.
August 4, 2021 – By Bruce Goldman
Ivan Soltesz and his colleagues have found that a marijuana-like compound in the brain calms epileptic seizures but also increases memory loss.
A marijuana-like chemical in the brain, mirroring its plant-based counterpart, packs both ups and downs.
Epileptic seizures trigger the rapid synthesis and release of a substance mimicked by marijuana’s most psychoactive component, Stanford University School of Medicine investigators have learned. This substance is called 2-arachidonoylglycerol, or 2-AG, and has the beneficial effect of damping down seizure intensity.
But there’s a dark side. The similarly rapid breakdown of 2-AG after its release, the researchers found, trips off a cascade of biochemical reactions culminating in blood-vessel constriction in the brain and, in turn, the disorientation and amnesia that typically follow an epileptic seizure.
The Stanford scientists’ findings, reached in collaboration with colleagues at other institutions in the United States, Canada and China, are described in a study to be published Aug. 4 in Neuron. Ivan Soltesz, PhD, professor of neurosurgery, shares senior authorship with G. Campbell Teskey, PhD, professor of cell biology and anatomy at the University of Calgary in Alberta, Canada. The study’s lead author is Jordan Farrell, PhD, a postdoctoral scholar in Soltesz’s group.
The researchers’ discoveries could guide the development of drugs that both curb seizures’ strength and reduce their aftereffects.
Electrical storm in the brain
About one in every hundred people has epilepsy. Epileptic seizures can be described as an electrical storm in the brain. These storms typically begin at a single spot where nerve cells begin repeatedly firing together in synchrony. The hyperactivity often spreads from that one spot to other areas throughout the brain, causing symptoms such as loss of consciousness and convulsions. It’s typical for the person experiencing a seizure to need tens of minutes before becoming clearheaded again.
The majority of epileptic seizures originate in the hippocampus, a brain structure buried in the temporal lobe, said Soltesz, the James R. Doty Professor of Neurosurgery and Neurosciences. The hippocampus plays an outsized role in short-term memory, learning and spatial orientation. Its ability to quickly adopt new neuronal firing patterns renders it especially vulnerable to glitches that initiate seizures. (Most epileptic seizures in adults begin in or near the hippocampus, Soltesz noted.)
In the study, Soltesz and his associates monitored split-second changes in levels of 2-AG in the hippocampus of mice during periods of normal activity, like walking or running, and in experiments in which brief seizures were induced in the hippocampus.
2-AG is an endocannabinoid, a member of a family of short-lived signaling substances that are the brain’s internal versions of the psychoactive chemicals in marijuana. 2-AG and these plant-derived psychoactive chemicals share an affinity for a receptor, known as CB1, that’s extremely abundant on the surface of neurons throughout the brain.
“There have been lots of studies providing evidence for a connection between seizures and endocannabinoids,” Soltesz said. “What sets our study apart is that we could watch endocannabinoid production and action unfold in, basically, real time.”
A brake on excitement
Endocannabinoids are understood to play a role in inhibiting excessive excitement in the brain. When excitatory neurons, secreting chemical “go” signals, exceed a threshold, they induce the production and release of endocannabinoids, whose binding to CB1 on an excitatory neuron acts as a brake, ordering that neuron to chill out a little.
While smoking marijuana floods the entire brain with relatively long-lasting THC, endocannabinoids are released in precise spots in the brain under precise circumstances, and their rapid breakdown leaves them in place and active for extremely short periods of time, said Soltesz, who has been studying the connection between endocannabinoids and epilepsy for decades.
But because endocannabinoids are so fragile and break down so quickly, until recently there was no way to measure their fast-changing levels in animals’ brains. “Existing biochemical methods were far too slow,” he said.
The most recent study had its start when Soltesz learned of a new endocannabinoid-visualization method invented by study co-author Yulong Li, PhD, a professor of neuroscience at Peking University in Beijing. The method involves the bioengineering of select neurons in mice so that these neurons express a modified version of CB1 that emits a fluorescent glow whenever a cannabinoid binds to the modified endocannabinoid receptor. The fluorescence can be detected by photosensitive instruments.
Using this new tool, the scientists could monitor and localize sub-second changes in fluorescence that correlate with endocannabinoid levels where that binding was occurring.
Zeroing in on 2-AG
By blocking enzymes critical to the production and breakdown of different endocannabinoids, the researchers proved that 2-AG alone is the endocannabinoid substance whose surges and rapid disappearance track neuronal activity in the mice. Several hundred times as much 2-AG was released when a mouse was having a seizure compared with when it was merely running in place.
The researchers were able to rule out the involvement of an alternative endocannabinoid, anandamide, that many neuroscientists and pharmacologists had assumed was the active substance. Anandamide’s name is derived from the Sanskrit word for “bliss.”
“This previously undetected activity-dependent surge in levels of 2-AG downregulates excitatory neurons’ excessive rhythmic firing during a seizure,” Soltesz said.
But 2-AG is almost immediately converted to arachidonic acid, a building block for inflammatory compounds called prostaglandins. The researchers showed that the ensuing increase in arachidonic acid levels resulted in the buildup of a particular variety of prostaglandin that causes constriction of tiny blood vessels in the brain where the seizure has induced that prostaglandin’s production, cutting off oxygen supply to those brain areas.
Oxygen deprivation is known to produce the cognitive deficits — disorientation, memory loss — that occur after a seizure, Soltesz said.
“A drug that blocks 2-AG’s conversion to arachidonic acid would kill two birds with one stone,” Soltesz said. “It would increase 2-AG’s concentration, diminishing seizure severity, and decrease arachidonic acid levels, cutting off the production of blood-vessel-constricting prostaglandins.”
Another Stanford co-author of the study is postdoctoral scholar Barna Dudok, PhD.
Other researchers at the University of Calgary, as well as researchers at Vanderbilt University, contributed to the work.
The study was funded by the National Institutes of Health (grants K99NS117795, MH107435, 1S10OD017997-01A1, NS99457 and NS103558), the Canadian Institutes of Health Research, the Beijing Municipal Science & Technology Commission, the National Natural Science Foundation of China, and the Peking University School of Life Sciences.
The use of cannabis to treat epilepsy and other neurological conditions has been studied for a number of years. It has been hotly debated too.
On June 25, 2018, the U.S. Food & Drug Administration (FDA) approved EPIDIOLEX ® (cannabidiol, CBD) oral solution for the treatment of seizures associated with two epilepsy syndromes – Lennox-Gastaut syndrome and Dravet syndrome – in people two years of age or older. Epidiolex represents a new medication option for children with these types of epilepsy. It is also the first ever FDA approved medication to treat seizures in Dravet syndrome.
What does FDA approval of Epidiolex (CBD oral solution) mean?
The FDA approval and Drug Enforcement Administration (DEA) scheduling of Epidiolex brings to market the first plant-based drug derived from the cannabis plant in the U.S.
What is medical cannabis?
Cannabis is known by many names – the most common is marijuana. Cannabis is the Latin name used most often by botanists and pharmaceutical companies. The word marijuana usually refers to the leaves and female flowers of the cannabis plant. Medical cannabis is whole plant marijuana or chemicals in the plant used for medical purposes.
Cannabinoids are substances in cannabis that act on cells in the body (called cannabinoid receptors) to cause some effect. Two major ingredients include
- Tetrahydrocannabinol, or THC, which causes the psychoactive effects of “getting high”
- Cannabidiol, or CBD, which does not cause psychoactive effects but has shown some positive effects on certain body systems. This is the part that has been effective in reducing seizures in some people with epilepsy.
Does cannabis help seizures?
Early evidence from laboratory studies, anecdotal reports, and small clinical studies over a number of years suggest that cannabidiol (CBD) could potentially help control seizures. Research on CBD has been hard to do and taken time due to federal regulations and limited access to cannabidiol. There are also many financial and time constraints. In recent years, a number of studies have shown the benefit of specific plant-based CBD product in treating specific groups of people with epilepsy who have not responded to traditional therapies.
What do I need to know about hemp?
Hemp is a variety of Cannabis Sativa L. plant historically grown for fibrous materials found in its stalks and seeds. It has been used to make items such as clothing fiber, upholstery, and other household items.
Hemp traditionally contains lower concentrations of THC and higher levels of CBD. Cannabinoids extracted from hemp plants, including CBD, have until recently been classified as marijuana and considered Schedule I substances. Per the DEA, Schedule I substances currently have no accepted medical use and have a high potential for abuse. A federal law* enacted in December 2018, however, reclassifies hemp and hemp-derived CBD as an agricultural commodity and exempts it from the list of Schedule I Drugs.
Despite this change in the classification of hemp and hemp-derived CBD, the only CBD product that has been rigorously studied and approved to be used as a medical therapy for epilepsy is the drug Epidiolex. While more CBD products may come to market in the coming months, it is important to understand that not every CBD product is the same quality or uniform from batch to batch. Any drug or supplement that is being considered for use as a medical treatment should first be discussed with your doctor. The potential for benefit as well as the interaction with other seizure medications and possible side effects require careful review with your doctor.
*The Agriculture and Nutrition Act of 2018 (H.R. 2) legalizes hemp and hemp-derived CBD. The bill changes the definition of hemp to encompass any plant or product derived from the plant that contain less than 0.3% THC by dry weight and classifies them as exempt from the controlled substance restrictions applied to marijuana. The law further amends the Controlled Substances Act to exempt hemp from Schedule I drugs.
What do I need to know about hemp?
Epidiolex (Cannabidiol, CBD)
Studies in the U.S. of Epidiolex (a plant-based CBD formulation) have been ongoing for a number of years. Data from these studies has helped provide evidence that led to the FDA approval of this product on June 25, 2018.
Epidiolex is a purified (> 98% oil-based) CBD extract from the cannabis plant. It is produced by Greenwich Biosciences (the U.S. based company of GW Pharmaceuticals) to give known and consistent amounts in each dose.
Researchers studied this medicine in controlled clinical trials. These studies used a control group with some people taking a placebo while others were given CBD at different doses. Researchers did not know who was getting the placebo and who was getting CBD. These tpyes of studies are called “gold standard” studies.
A summary of the Epidiolex clinical trials is found below:
- In controlled and uncontrolled trials in people with Lennox-Gastaut syndrome (LGS) and Dravet syndrome, 689 people were treated with Epidiolex (CBD), including 533 people treated for more than 6 months and 391 people treated for more than 1 year.
- In an expanded access program and other compassionate use programs, 161 people with Dravet syndrome and LGS were treated with Epidiolex, including 109 people treated for more than 6 months.
- All study participants were taking other seizure medications.
- In controlled trials, the rate of stopping the medicine due to any side effect was small and happened most in people taking the higher dose of Epidiolex.
- The most frequent cause of stopping treatment with Epidiolex was a change in liver function.
- Sleepiness, sedation, and lethargy led to stopping Epidiolex in 3% of people taking the higher dose.
- The most common side effects were sleepiness, decreased appetite, diarrhea, change in liver function, fatigue, malaise, asthenia (weakness or lack of energy), rash, insomnia, sleep disorder, poor quality sleep, and infections.
Results from Gold Standard Studies of Epidiolex (CBD)
NEJM May 2018
Summarized below are the results from a study published in the New England Journal of Medicine in May 2018.