Day 7 Virginia Thornley, M.D., General Neurologist and Epileptologist
February 16, 2018
Cannabidiol (CBD) is the little known medical component without the euphoria used for medical indications such as analgesic, anti-inflammatory, anti-epileptic and anxiolytic effects. In the pathway for endocannabinoids, cannabinoid exerts its therapeutic effects by binding to the CBD1 receptor found in the brains and the nerves exerting their analgesic effects. CBD does not have the same euphoriant effect as THC its counterpart which is better known to the public with much stigma. CBD will need to be 100 times more potent to have the same euphoria as THC making it relatively safe to give without the intoxicating effects. THC or delta-tetrahydrocannabidiol is the main psychoactive component in the marijuana plant, the one finds in the street drugs which has caused such a stigma shadowing the beneficial effects of the plant. Cannabidiol is also thought to work on the 5HT1 receptor giving its anxiolytic properties. This review seeks to understand some of the laboratory research that study the underlying mechanisms for its beneficial actions.
Cannabidiol works on CBD1 receptor and is thought to have an analgesic and anti-inflammatory role in diseases. In many states, it still outlawed to have in possession but growing clinical evidence shows that it can be used in pain syndromes. In the state of Florida there are 10 conditions recognized that can be treated with CBD. It is most commonly used in pain from stage IV metastatic cancer. Cannabidiol has been found to have anti-inflammatory, anti-tumorigenic, analgesic, anti-epileptic and anxiolytic properties.
CB1 receptors are found to be expressed in anterior horn cells. The CB2 receptors possibly reduce pain by acting on the neutrophil accumulation and mast cell degranulation which can reduce pain both of these processes increase inflammatory algesia(1).Analgesia has been demonstrated with cannabinoids in visceral inflammation and pain due to peripheral neuropathies, important areas of therapeutic considerations.
Some of the vast scientific research for cannabinoid is found in the animal models for epilepsy. Cannabinoids exert effects on CB1 and CB2 receptors in the hippocampus where it has a weak affinity(5). CBD1 receptors affect transmission in the synapses through the voltage-gated calcium and potassium channels. There are studies on the effects of CBD in refractory types of epilepsy such as Dravet’s syndrome one of the SCN1a genetic disorders affecting the sodium channel manifesting as severe myoclonic epilepsy. Mechanisms of CBD include increasing excitation of the inhibitory effect of the hippocampus where seizures are propagated. At low doses, it helps with autism and impaired cognition. It may exert its effect by working against GPR55(7), TRPV1 in addition to voltage-gated voltage-gated potassium and sodium channels. Another study supports the role that cannabinoids may play in shifting the inhibition of glutamatergic effects and GABAergic effects in the hippocampus mediated by CB1 receptors. In the rat model, it was suggested that seizures can upset the balance of these glutamate and GABA systems (4). 15 minutes after an induced seizure, there is increased 2-arachidonylycerol which is a CB1 agonist suggesting cannabinoids act as a negative feedback loop for seizures(4). In addition, it was found there are more CB1 receptors in the hippocampi with induced seizures compared to control suggesting plasticity of the brain with a compensatory increase in CB1 receptors in response to increased seizures(4). CB2 receptors are related to the immune system and are limited in the CNS. Cannabinoids affect calcium homeostasis and may provide its neuroprotective effects. Growing evidence shows case series, case reports and anecdotal reports on patients having fewer seizures on cannabidiol. Large case-controlled clinical randomized trials are needed.
There appears to be increased cancel cell death, reduced viability and reduced numbers of metastatic cells. In one study, it is found to reduce epidermal growth factor-induced multiplication and chemotaxis of cells in breast cancer. In mouse models, it inhibits macrophage recruitment in tumor-related cells.n It can potentially inhibit metastasis and proliferation and may provide a novel therapeutic option in breast cancer(2).
It works on the 5HT1 receptor by altering effects on this receptor the exact mechanism is unknown accounting for anxiolytic properties(6).
CBD may alter the effects of THC and reduce its psychoactive properties (6).
Alternative treatment in opioid use
CBD might also work in place of opioids with the growing epidemic of chronic pain and overuse of opioids, CBD may be an alternative analgesic for chronic pain without the effect of tolerance or sedating properties. CBD was found to reduce the reward effects of morphine and does not have the same properties of tolerance. CBD does not have the same euphoria and THC and works on pain(6).
In summary, it is an exciting time for research in the use of cannabinoids. There are innumerable basic science research studies demonstrating the therapeutic effects at the cellular level. Large randomized clinical trials are still needed to gain information in using cannabinoids in humans.
- Rice, AS, et al, “Endocannabinoids and pain: peripheral and spinal analgesia in inflammation and neuropathy, ” Prostaglandins, Leukotrienes and Essential Fatty Acids, 2002, Feb., 66(2-3)246-256.
- Elbaz, E. et al, ” Modulation of tumor microenvironment and inhibition of EGF/EGFR pathway: novel mechanisms of Cannabidiol on breast cancer,”Molecular Oncology, 2015, Apr., 9(4):906-919.
- Welty, W.E., et al, “Cannabinoids: the promises and pitfalls,” Epilepsy Currents, 2014, Sep.-Oct., 14(5):250-252.
- Wallace, MJ, et al, ” The endogenous Cannabinoid system regulates seizure frequency and duration in a model of temporal lobe epilepsy, ” The Journal of Pharmacology and Experimental Therapeutics, 2003, Oct., 307(1):129-137.
- Gaston, T. et. al, “Pharmacology of cannabinoids in the treatment of epilepsy, ” Epilepsy Behavior, 2017, May, 70:313-318.
- Volkow, Nora, “The biology and potential therapeutic effects of cannabidiol,” National Institute on Drug Abuse Senate Caucus on International Narcotics Control, 2015, June.
- Kaplan, et.al, “Cannabidiol attenuates seizures and social deficits in a mouse model in Dravet syndrome, “Proceedings of the National Academy of Science, 2017, Oct.
Virginia Thornley, M.D., completed an Internship at University of Virginia Residency University of Vermont in Neurology and Fellowship in Clinical Neurophysiology and Epilepsy fellowship at the University of Rochester. She is currently a General Neurologist in private practice in the southwest.