Learn about CBD oil, vapor and pills as a treatment for Alzheimer’s disease and other dementias. The Effect of Cannabidiol (CBD) on the Short-Term Memory of young Drosophila melanogaster Research that is focused on memory is prominent in modern times because age-related memory loss is a
Using CBD (Cannabidiol) to Treat the Symptoms of Alzheimer’s & Other Dementias
CBD (aka Cannabidiol) is a compound derived from the Cannabis plant that has positive medicinal effects but does not make people feel “high” or anxious. CBD, in various forms, is legal in 48 US States. The states where it remains illegal are Idaho, and South Dakota, though in SD it will be legal beginning in July 2021. For much more on legality, see below.
CBD should not be confused with Marijuana or the THC (Tetrahydrocannabinol) compound which is known for generating a “high” with users. CBD is derived from Cannabis plants, similar to how caffeine is derived from the coffee bean, or aspirin from the bark of a Willow tree. CBD oil is the most common form of administration of the compound, with the oil contained in a gel cap or dropper bottle.
Another chemical in cannabis plants that shows medical benefits similar to CBD is called cannabigerol, or CBG. CBG comes from young marijuana plants and, like CBD, does not get users high. CBG may be useful for treating a specific type of dementia called Huntington’s disease. For more, see below.
CBD Health Benefits for Dementia
The dementia-related conditions that can be helped by CBD include: Alzheimer’s disease, Vascular Dementia, Dementia with Lewy bodies (DLB), Parkinson’s disease, Frontotemporal dementia and Huntington’s disease.
According to researchers at California’s Salk Institute, their 2016 study found evidence that cannabinoids such as CBD could help remove dementia from, and increase connections between, brain cells. Those results were validated by other laboratories. While the US Food and Drug Administration has yet to approve a CBD drug for the purposes of treating dementia, it has approved a CBD-based drug called Epidiolex for treating epilepsy.
There are several ways CBD can work to improve health outcomes for persons with dementia: by reducing inflammation, by reducing oxygen buildup, by working as a brain stimulant and neuroprotectant, and by eliminating dead brain cells and the protein tangles that are believed to cause brain ailments including dementia. From a user’s perspective, CBD may improve movement while reducing stress and anxiety in the individual with dementia, as well as reduce the decline of memory and other brain functions.
It should be noted that controversy surrounds CBD and the claims companies have made as to its positive effects. The FDA warns that CBD can cause liver injury (as shown in some animal experiments with super high doses) and affect metabolism of other drugs. The agency also says that long-term side effects remain unknown because it has not been studied for a long enough period of time. In actions that are politically based instead of scientifically, the FDA has not approved the use of CBD.
The topic of CBD health benefits continues to grow with new CBD and Alzheimer’s research. In recent studies, CBD has been shown to reduce or remove the impact of inflammation, oxygen buildup and brain cell decline. CBD also increases levels of proteins that eliminate dead cells and plaques in brains with Alzheimer’s, improving both memory and motor function.
When the brain’s immune cells fail to clear blockages associated with Alzheimer’s disease, the result is an inflammatory response. When inflammation happens in the brain, oxygen is released as a result. The greater the inflammation, the greater the negative impact. Important brain functions such as memory are decreased as more oxygen is released in the brain’s cells. Memory loss and other brain deterioration indirectly leads to increased oxygen in the brain. CBD is an antioxidant, which helps reduce the problems associated with oxygen stress. Brain functions negatively impacted by oxygen stress can be improved by using CBD.
Alzheimer’s patients’ brain cells often show a path of rapid decline and destruction. The potential of stimulating brain tissue was recently discovered as a potential benefit of CBD. In clinical trials, CBD has shown the ability to reverse and even prevent the development of Alzheimer’s negative impact. A 2011 study by Australian researchers Tim Karl and Carl Group found that CBD promotes the growth and development of brain cells, reducing the decline of memory and other brain functions.
More recently, in a study researchers were able to increase levels of proteins in the brain (called IL-33 and TREM2) that maintain cognitive functions by eliminating dead cells and helping clear beta-amyloid plaque tangles associated with the disease. After CBD was regularly injected into mice afflicted with Alzheimer’s disease, scientists noticed major improvements in their ability to think. Specifically, the mice could better tell the difference between old objects and new ones. The mice’s movement improved, as well. People with Alzheimer’s often develop stiffness that affects their ability to walk, and mice with these same symptoms will continuously walk in a tight circle. After CBD treatments, that behavior stopped.
Vascular dementia is a general term describing problems with reasoning, planning, judgment, memory and other thought processes caused by brain damage from impaired blood flow to one’s brain. To effectively treat vascular dementia, a 2016 study by the US National Institute of Health (NIH) found that activating CB2 (cannabinoid) receptors in the brain helped recover better blood flow to the brain. Activating the CB2 receptors with CBD has increased brain cell activity and helped reduce brain cell damage commonly associated with vascular dementia.
Dementia with Lewy Bodies
Lewy body dementia (LBD) is a disease associated with abnormal deposits of a protein called alpha-synuclein in the brain. These deposits, called Lewy bodies, affect chemicals in the brain whose changes, in turn, can lead to problems with thinking, sleeping, movement, behavior, and mood. Unlike most pain, anxiety or behavior management drugs, CBD does not block acetylcholine, the main chemical that LBD attacks. Research has shown that CBD can be an effective anti-inflammatory agent, reduce motor symptoms (tremor, rigidity, bradykinesia) and maintain circadian (sleep) rhythms.
Parkinson’s is a chronic progressive disease of the nervous system chiefly affecting middle-aged and elderly people. Parkinson’s is linked to decreased dopamine production and marked by tremor, muscular rigidity, and slow, imprecise movement. Digestive imbalance may also play a role in the progression of Parkinson’s and the severity of symptoms. Cannabinoids such as CBD have been shown to contain effective brain protectors, antioxidants and anti-inflammatory properties which can be beneficial for managing Parkinson’s disease. Read more about Parkinson’s and CBD.
Frontotemporal Dementia / Pick’s Disease
Frontotemporal dementia (FTD) or frontotemporal degenerations refers to a group of disorders caused by progressive nerve cell loss in the brain’s frontal lobes (the areas behind one’s forehead) or its temporal lobes (the regions behind one’s ears) that leads to symptoms of depression and psychosis. Unlike most antipsychotic drugs, CBD does not lead to an increased risk of death. Research has shown that CBD can be an effective anti-inflammatory agent, reduce anxiety, reduce motor symptoms (tremor, rigidity, bradykinesia) and maintain circadian (sleep) rhythms.
Huntington’s disease (HD), also known as Huntington’s chorea, is an inherited disorder that results in death of brain cells. The earliest symptoms are often subtle problems with mood or mental abilities. A general lack of coordination and an unsteady gait often follow. According to 2016 research from the University of Madrid, due to CBD’s effectiveness as antioxidants and its anti-inflammatory properties, CBD can be beneficial for managing Huntington’s disease. Experiments with mice have shown that another chemical called cannabigerol, or CBG, in marijuana plants can help maintain brain health for people with Huntington’s (see next section).
What is CBG? (CBG vs. CBD)
Another cannabinoid (compound in cannabis) that has shown health benefits is cannabigerol, also known as CBG. Often taken as an oil, like CBD, CBG is rarer than CBD and THC because there is much less of it in a plant. Whereas cannabis strains usually contain about 25% THC and 20% CBD, the compound CBG makes up only about 1% of most plants. CBG can, however, be extracted at higher volumes if the plants are harvested at the right age, meaning younger. CBG turns into CBD and THC as the plant gets older.
CBG binds to cannabinoid receptors in the body, strengthening neurotransmitters (brain cells) that specifically function to do things like motivate us and regulate our appetites and sleeping patterns. Studies have even shown that CBG protects nerve cells in the brain.
Unfortunately, those studies were done on the brains of mice, not humans (specifically, mice with an experimental model of Huntington’s disease). There are actually fewer studies on CGB in humans than the other cannabinoids, so while there is a strong case to be made that CGB works as a neuroprotectant that preserves nerve cells in the brain, the evidence is slimmer.
Like CBD, CGB is non-psychotropic and won’t get you high. A key difference between CBD and CBG is that CBG is harder to extract and therefore more expensive.
Risks & Side Effects
The World Health Organization (WHO) stated that “no public health problems… have been associated with the use of pure CBD,” and there has been no known association with potential for dependence or abuse, unlike most pharma alternatives. The most commonly reported potential side effects of CBD usage were diarrhea and bloating, with some also reporting nausea. About 3% of patients in studies reported liver problems and had to discontinue CBD use. Specifically, in dementia, some patients reported increased tremor with high doses of CBD. As with any new treatment, patients and caregivers should monitor effects and outcomes closely.
Full-Spectrum vs. Isolated CBD
CBD comes in either “full-spectrum” or “isolated” form. The difference is that full-spectrum includes other compounds besides just CBD: cannabinoids (THC and others), terpenes (plant chemicals), and flavonoids (natural plant antioxidants). CBD isolate has been processed into a powder without those natural chemicals. Full-spectrum has more health benefits than isolate.
Misperceptions & Myths
1) CBD is non-psychoactive and medicinal while THC is recreational, not medicinal
CBD (cannabidiol) has been shown to have antipsychotic and anti-anxiety effects in humans. This does not mean it is non-psychoactive, but rather that the psychoactive effects are often beneficial and non-intoxicating vs. the “high” feelings of the THC (aka Tetrahydrocannabinol) compound. THC has also shown medicinal benefits for patients, particularly those suffering from pain or inflammation, especially when combined with CBD for consumption by patients.
2) CBD is a sedative and reduces awareness or alertness
Even in high doses (600mg), CBD has not produced sedating effects in healthy humans. CBD usually makes humans feel more awake and alert without negative impact on sleeping patterns. What is more likely happening is that cannabis strains being used by a patient that have high levels of CBD also contain a potentially sedating natural oil (terpene) such as myrcene.
3) All CBD sources are the same
There are multiple sources of CBD such as hemp, medical cannabis and isolate. Hemp-based CBD is plagued by mislabeling and recent studies have found that only 31% of 84 tested hemp-based CBD products were accurately labeled. Medical, locally sourced cannabis has consistently produced the best CBD source as it is held to stricter laboratory testing for potency and contaminants. If you’re ordering CBD online, know that mislabeling is common, and look for products that have been third-party tested, meaning independent testing has shown the stated percentages are correct.
4) CBD is legal in all 50 States
Despite CBD being sold in health food stores, tobacco shops, on Amazon, etc., and legalization by many US States, the Federal government has not legalized CBD-rich medical cannabis. Hemp-based CBD (with less than 0.3% THC) would not technically have this restriction because it is legal at the state and federal level everywhere except for South Dakota and Idaho. In these two states, CBD is only legal with zero THC. Medical-based CBD has been legalized in more than 30 states and is recreationally legal in a growing number of US locations.
Avoid CBD Scams! Legitimate CBD products will be precisely labeled with information including:
– Amount of active CBD per serving
– Other ingredients
– Manufacturer name
– Suggested use
– Lab testing results
Every batch of CBD should be tested before it’s put into stores to sell.
Forms of CBD Administration
CBD comes in many forms. They range in variety from being consumed orally, inhaled or absorbed into the skin. The most popular are:
-Oil (either to go on the skin or under the tongue)
-Patches (like Band-Aids)
Vape Pen Danger – CBD oil in vape pens sometimes contains a solvent called “propylene glycol,” which degrades when burned at high temperatures and can have serious side effects. Look for “solvent free” CBD vape pens.
|Forms of CBD Administration|
|Form||Time Until Effects Are Felt||Duration of Effects|
|Oral: via Pill or Liquid Drops||15-90 minutes||4 hours|
|Skin: via Oil or Patches (like Band-Aids)||15-120 minutes||5 hours|
|Inhaled: via Vaporizer||2-3 minutes||1 to 2 hours|
Legal Status of CBD in the U.S. (as of May 2022)
CBD is widely available and can be found anywhere from local health food stores and tobacco shops to online retailers like Amazon; making it unclear as to its legality. In 2018, the U.S. legalized CBD through the Farm Bill. That gave a national legal standard with guidelines dictating it contains less than 0.3% THC and made from hemp (not marijuana). Because of differences between state and federal laws, each state can have their own requirements on its legality.
In spite of the diverse legal status in different states, CBD can be purchased online and delivered legally to all 50 states.
A table below breaks down the different requirements by state (as of May 2022) to CDB’s legality.
|Legality of CBD by State (Updated May 2022)|
|Conditions of Legality||States in which these Conditions Apply|
|CBD and medical cannabis is legally available to all adult users (21+)||Alaska, Arizona, California, Colorado, District of Columbia, Illinois, Maine, Massachusetts, Michigan, Nevada, New Jersey, Oregon, Vermont and Washington.|
|CBD and medical cannabis is legally available by prescription only||Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Hawaii, Iowa, Louisiana, Maryland, Minnesota, Missouri, Montana, New Hampshire, New Mexico, New York, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, Utah, Virginia, West Virginia, Wisconsin and Wyoming.|
|CBD with limited THC content (less than 0.3%) and made from hemp is legally available||Indiana, Kansas, Kentucky, Mississippi, Nebraska, South Carolina, North Carolina, Tennessee and Texas.|
|CBD with zero THC and made from hemp is legally available||South Dakota and Idaho.|
CBD can also be used legally in most states by residents of assisted living and memory care communities. Read more.
FDA Approval Under Consideration
Not giving CBD federal approval made lawmakers write a bill that would force the FDA to do so. Introduced in early 2021, H.R.841 would make hemp and its byproducts legal and labeled as a dietary supplement under the FDA’s protection and jurisdiction.
This potential law is important for two major reasons. First, FDA approval is the key to making it more accessible to patients in all states and all care facilities. In addition, this leads to potentially being covered by insurance as Medicare and Medicaid have set precedence that they normally approve coverage for all FDA approved medicines.
At this point, it is unknown if this Bill will make a difference. H.R.841 has a long time before it will be signed into law; it is estimated at two years before the FDA is forced to decide on CBD’s legality.
The most common means to obtain CBD rich medical marijuana is from a state licensed dispensary. These dispensaries can be found by searching on any number of dispensary directories (Leafly, Yelp, etc.) or Google Maps.
For those that have trouble with transportation, another increasingly available option would include delivery-based options. However, while convenient for senior patients, these options are not available in every city or town.
Finally, CBD can be legally purchased over the Internet and delivered to all 50 states. One reputable seller is CBDPure. One can visit their website here.
Given the lack of regulation in the CBD marketplace and given the challenges of self-reporting of the benefits with persons with dementia, getting the CBD dosage correct is especially challenging. Even though no prescription is required to purchase CBD, many doctors are still knowledgeable about the product and can provide dosage recommendations. Furthermore, given many persons with dementia take multiple medications, it is worth researching drug-drug interactions when considering CBD. CBD dosage consultations can be arranged online with a doctor for about $60. This is a preferable approach to proceeding without professional medical input. However, it is unlikely one’s insurance would pay for these online dosage consultations.
Should one proceed in testing CBD’s impact on a loved one’s dementia, it’s best to start with the gel cap form of administration as the levels of CBD are consistent (when compared to a dropper) and the act of swallowing a pill is familiar. A further benefit is the once-daily scheduling. While many of CBD’s hypothetical benefits cannot be easily observed, loved ones should pay careful attention to behavior changes. People with dementia who appear calmer or experience less severe sundowning symptoms may be benefitting from CBD. Another area in which CBD’s impact may be observed is in reducing sleeplessness.
Finding the Right Dose
It’s a good idea to start small and slowly increase the dosage. Begin with between 1 and 2 milligrams per day for one week, and increase by 2 to 3 milligrams weekly until you notice improvements in symptoms. Base the dosage on body weight: go smaller if your loved one is particularly light, and give a slightly larger dose for a heavier person. A normal dose for an average adult is around 5 milligrams. You may not want to exceed that number. Again, consult a doctor as you would with any other new supplement or medication.
Insurance Coverage of CBD
At this early stage of development, there are few options covered by insurance. The Food and Drug Administration would need to sign off, and as of now there is only one CBD drug (Epidiolex, for epilepsy) with FDA approval. New legislation is in congress that would force the FDA’s approval. However, currently, when compared to the prices of alternative pharmaceuticals, patients and caregivers may still find that CBD-based medical marijuana is a more cost effective and safer option.
Does Medicare cover CBD? Because of the federal prohibitions on prescribing Schedule 1 substances, there is no Medicare coverage for the purchase of medical marijuana or CBD derivatives. Any out-of-pocket costs one would incur purchasing marijuana for medical use will not count toward any deductibles under Part B or a Medicare Prescription Drug Plan. If congress will pass H.R.841 that will force the FDA to decide on CBD. In that case, coverage could potentially change to include it.
Medicinal cannabis is not covered by Medicaid, private plans, group plans, the Veterans Administration (VA) or Obamacare plans. Again, when FDA approval happens there could be coverage of CDB.
The Effect of Cannabidiol (CBD) on the Short-Term Memory of young Drosophila melanogaster
Research that is focused on memory is prominent in modern times because age-related memory loss is a growing issue throughout the world. Previous research has suggested that cannabidiol (CBD) can improve the memory of the elderly suffering from neurodegenerative diseases. However, the effect that CBD has on the memory of young people has not been extensively studied. Here we show that CBD does not improve the short-term memory of young male D. melanogaster. Our finding has contradicted the known knowledge of how CBD could potentially be used for memory loss. Our results suggest that exposure to CBD may result in impairment of the short-term memory and cause erratic behavior in young organisms. These outcomes could be a starting point for future study on the effect that CBD may have on young humans.
Memory plays a major role in adapting to a habitat and acquiring various skills. Learning is essential for memory, and memory allows organisms to recall the information they learned and use it whenever they need to. There are two main types of memories pertaining to humans: long-term and short-term memory (Cowan, 2008). Long-term memory is a remembrance of events that have taken place at an early time of one’s life and cannot be forgotten easily. Short-term memory is the remembrance of actions or events that have occurred recently and can be forgotten quickly (Cowan, 2008). There are important factors that can cause damage to short-term memory such as aging, physical injury, and substance abuse. Short-term memory impairment increases as humans age. Throughout the world, there is an estimate of 50 million people with dementia. This number is expected to grow by 10 million cases every year (World Health Organization, 2020).
Substance abuse has been a growing issue throughout the world. One of these substances is Cannabis, found in the Cannabis sativa plant, and is commonly known as Marijuana. Two major components found in Cannabis are Cannabidiol (CBD), which is not a mind-altering component and Tetrahydrocannabinol (THC), which is a mind-altering component (Schoeler and Bhattacharyya, 2013). CBD has several positive effects on the human body, such as reducing neuroinflammation, reducing brain damage caused by neurodegenerative diseases, promoting the production of new neurons in the brain, and raising levels of synaptic plasticity in the brain (Maroon and Bost, 2018). However, there are negative effects of CBD which include irritability, extreme tiredness, and nausea (Grinspoon, 2018). Previous studies have stated that CBD can improve the memory of people over the age of 65 with neurodegenerative diseases (McGuire et al., 2017). Currently, there is not a large amount of research on how CBD affects the memory of people under the age of 25 years old.
The current study aims to test if CBD improves the short-term memory of young male Drosophila melanogaster, commonly known as fruit flies. This organism is ideal for this study as it is easy to maintain, and it reproduces fairly quickly. Drosophila also have a short life span, which allows us to study short-term memory in a limited period of time. We hypothesized that exposure to CBD may improve the short-term memory of the male D. melanogaster when the aversive phototaxic suppression assay (APSA) is performed.
Materials & Methods
Fly stock and rearing conditions
A wildtype D. melanogaster Oregon R is used in this study. Flies were reared in tubes containing cornmeal media. They were flipped into fresh media every three weeks and were kept in a 20oC chamber. For this study, we used flies that were up to two weeks old.
Pilot Study: Testing the Amount of CBD To Use
Prior to performing the experiment, the amount of CBD oil (Fisher Scientific, 1 mg/mL CBD in 1 mL ethanol or methanol) that the flies were exposed to was determined by exposing the flies to fly food that contained differing amounts of CBD. The flies consumed food that contained 0.4 mL, 0.2 mL, 0.1 mL, 0.075 mL, or 0.050 mL of CBD. The CBD was mixed into the food along with 2 mL of water. Based on our data, we decided that 0.050 mL of CBD (0.025 M CBD solution) was appropriate for our experiment. The control was the same amount of ethanol without CBD.
Pilot Study: Testing the Experimental Apparatus
Figure 1. This apparatus used for the phototaxis test and APSA test. Quinine hydrochloride solution was applied on the inside of the lighted tube (left). It was used to test whether the fly was sighted or not, was used for the learning and short-term memory tests.
The efficiency of the experimental apparatus we made for the current study was tested (Fig.1). Tube 1 contained 1.8 g of fly food, 2 mL of 1MΩ water, and 0. 05 mL of CBD solution. Tube 2 contained 1.8 g of fly food, 2 mL of 1MΩ water, and 0.05 mL of 95% ethanol as the control. The fly food containing ethanol was used as our control because the CBD was dissolved in ethanol. The students transferred 3 young flies into each tube, so they were exposed to these food conditions for 24 hours, and then the Aversive Phototaxic Suppression Assay was performed on each fly for 6 trials.
Your browser does not support the video tag.
The phototaxis test examines an organism’s innate ability to move towards light (Nakamura and Yamashita, 1997). Each fly was transferred into a dark tube, which was covered in aluminum foil, and then the room was made dark. The fly was allowed to acclimate to the dark for 1 minute. Another tube was then connected to the dark tube, and a light was flashed from above on to the tube that was not covered in aluminum foil (lighted tube). The fly was given the option to move to the lighted tube or stay in the dark tube. The fly that was positively phototaxic moved towards the light (Nakamura and Yamashita, 1997) if they were sighted within 30 seconds. We performed the phototaxis test to eliminate the blind flies (or those with abnormal visual function) for the APSA.
Aversive Phototaxic Suppression Assay (APSA)
Your browser does not support the video tag.
This test trained the fly to remain in the dark side of the apparatus (Seugnet et al., 2009). Prior to the Aversive Phototaxic Suppression Assay (APSA), the flies were exposed to either diets (CBD-infused food or control food) for 24 hours. Then they were starved for 6 hours before starting the Aversive Phototaxic Suppression Assay. In this assay, two plastic tubes were used, one was covered in aluminum foil to create darkness and the other one was left uncovered. The uncovered tube was coated with a 1M solution of quinine hydrochloride, a bitter substance that repels the flies (Hayes et al., 2015). Each fly was transferred to the dark tube, the room was made dark, and the fly was allowed to acclimate to the dark for 1 minute. The uncovered tube containing quinine was then connected to the dark tube. A white light from a smartphone device was flashed on the uncovered tube and immediately a timer was started when the two tubes were connected. The timer was stopped once the fly touched the quinine on the lighted side of the tube. The students performed 10 trials and after each trial, the fly was tapped back into the dark tube and was allowed to rest for 30 seconds and re-acclimate to the darkness. After the learning test was performed, the flies were starved again for 6 hours so that their short-term memory could be tested. The memory test was just one trial. It is the same procedure as the learning test to determine if the flies remember what they had learned 6 hours ago.
First, we measured how many trials it took for the young male flies to learn. To do this, we performed the APSA (Materials and Methods). During the 10 trials, the flies exposed to the control food did not show a significant change until the 7th trial (Fig. 2b). There was a significant difference after the 8th trial. We interpreted this as the flies in the control group learned at the 8th trial. In the CBD treatment group, we found that the flies did not show a significant change throughout all 10 trials (Fig. 2c). We interpreted this as the flies in the CBD group did not learn at all.
We found that there was a wide variation of average avoidance times for each trial. (Fig. 2c) This could be the result of the CBD effect on the flies. We observed that some of the young male flies that were exposed to the CBD-infused food had very erratic behavior, which is described by abnormal movements of the flies, while others had sluggish or normal behavior. This could explain why the average avoidance times varied.
Second, we tested the effect of CBD on their short-term memory. To do this, the flies were starved for 6 hours and then the APSA was repeated once (Materials and Methods). We found that the flies exposed to the control food did not surpass the threshold avoidance time (Table 1). We interpreted this as the flies not remembering what they had learned. In the CBD treatment group, we could not calculate a threshold avoidance time because the flies did not learn throughout the 10 trials of the learning test. Therefore, since the flies did not learn, it is impossible for them to have remembered.
Table 1: Table shows the results of the memory test for flies exposed to control and CBD-infused food. The threshold avoidance time for the control group was 112.9 s. The threshold avoidance time was calculated by taking the average of the averaged trials that the flies learned in. (Threshold for control flies: average of the mean trials 8, 9, and 10). The flies whose avoidance times passed this threshold remembered what they learned. According to the learning test results, none of the control flies remembered what they learned. The flies exposed to CBD-infused food did not learn, so they do not have a threshold avoidance time. Since the flies did not learn, they did not remember.
This study focuses on the effect of CBD on young male D. melanogaster’s short-term memory. In order to do this, APSA was performed to observe whether a CBD-infused diet improved their learning or not. Using the APSA, 10 trials were conducted for the learning test, and then a 6-hour starvation gap was given before performing only one trial of the APSA again to test their memory. Figure 2 shows the results of the APSA tests for the control and CBD treated flies. We hypothesized that the CBD group would learn quicker than the control group. However, our results showed that the flies in the CBD group did not learn at all. Fig.1b shows a graph of the 10 trials of the learning test for the flies exposed to control food. The results of the Kruskal-Wallis test showed that trials 1-7 showed no significant learning in the flies (p>0.05), and trials 8-10 showed no significant learning in the flies (p>0.05). A Mann-Whitney test was done comparing trials 1-7 to trials 8-10 (p<0.05). This shows that the flies did not learn at the 8th trial as the control flies did. Also, since the results of the learning test in the CBD treated flies was erratic, we concluded that the flies did not learn at all during the 10 trials.
Fig.1c shows a graph of the 10 trials of the learning test for the flies exposed to CBD-infused food. The results of the Kruskal-Wallis test showed that trials 1-7 had no significant learning in the flies (p>0.05), and trials 8-10 showed no significant learning in the flies (p>0.05). A Mann-Whitney test was done comparing trials 1-7 to trials 8-10 (p>0.05). This shows that the flies did not learn at the 8th trial as the control flies did. Also, since the results of the learning test in the CBD treated flies was erratic, we concluded that the flies did not learn at all during the 10 trials.
Figure 2: Results of the Phototaxic Suppression Assay. a) Graph comparing the average avoidance times for each trial in the learning tests for male D. melanogaster in the control and CBD diets. b) Graph showing the 10 trials of the learning test for the flies exposed to control food (n=3). The p-values show that the flies learned at trial 8 (p<0.05). c) Graph showing the 10 trials of the learning test for the flies exposed to CBD-infused food (n=4). The p-values show that the flies did not learn at any trial.
Finally, we repeated one trial of the APSA 6 hours after the learning tests to determine if the flies remembered what they had learned. The threshold avoidance time for the flies exposed to the control food was 112.9 seconds (Table 1). Since none of the flies exposed to the control food surpassed the threshold avoidance time during the memory test, we conclude that none of them remembered what they had learned. A possible reason for this could be that the ethanol had a psychiatric effect on the flies that impaired their short-term memory. For the CBD group, it was impossible to calculate a threshold avoidance time because they did not learn. As a result, we cannot make conclusions about the CBD treated flies’ memory since they did not learn. However, it is interesting to note that fly 1 and fly 2 had a higher avoidance time compared to fly 3 and fly 4 (Table 1). Here, 2 groups can be seen, one group where there is high avoidance time and one group where the avoidance time is low. We assume there may be a psychiatric effect on each fly causing each one to behave differently compared to another fly. The CBD may not be 100% pure and may contain another major component of cannabis called tetrahydrocannabinol (THC) which has a mind-altering effect. This may be a reason why the flies behaved in a contrasting manner. Another factor could be that the flies may have had a genetic variation that was contributing to affecting each fly differently.
We conclude that CBD has an inhibitory effect on the short-term memory of male Drosophila melanogaster as they did not learn during the learning test nor did they remember during the memory test. We found that time was an essential component to perform this experiment. We were also researching other variables such as sex difference and age difference, but our sample size was too small due to the death of many flies.
The authors would like to thank Dr. Kwangwon Lee and Dr. Nathan Fried for their guidance and support, Sarah Johnson for ordering supplies, Taqdees Gohar for assisting with the experimental plan, and Harjit Khaira for providing fly supplies and advice.
Hayes, J.E., Feeney, E.L., Nolden, A.A., and McGeary, J.E. (2015). Quinine Bitterness and Grapefruit Liking Associate with Allelic Variants in TAS2R31. Chem. Senses 40, 437–443.
Ki, Y., and Lim, C. (2019). Sleep-promoting effects of threonine link amino acid metabolism in Drosophila neuron to GABAergic control of sleep drive. ELife 8, e40593.
Nakamura, T., and Yamashita, S. (1997). Phototactic Behavior of Nocturnal and Diurnal Spiders: Negative and Positive Phototaxes. Zoolog. Sci. 14, 199–203.
Seugnet, L., Suzuki, Y., Stidd, R., and Shaw, P.J. (2009). Aversive phototaxic suppression: evaluation of a short-term memory assay in Drosophila melanogaster. Genes Brain Behav. 8, 377–389.
Wong, R., Piper, M.D.W., Wertheim, B., and Partridge, L. (2009). Quantification of Food Intake in Drosophila. PLoS ONE 4.
McGuire, P., Robson, P., Cubala, W.J., Vasile, D., Morrison, P.D., Barron, R., Taylor, A., and Wright, S. (2017). Cannabidiol (CBD) as an Adjunctive Therapy in Schizophrenia: A Multicenter Randomized Controlled Trial. AJP 175, 225–231.
Schoeler, T., and Bhattacharyya, S. (2013). The effect of cannabis use on memory function: an update. Subst. Abuse Rehabil. 4, 11–27.