Cannabinoids may slow vision loss associated with degenerative diseases of the back of the eye, whether hereditary or age-related. They might even give eyesight!
This is what suggested by the preliminary results of a study by Joseph Bouskila, doctoral student at the School of Optometry at the University of Montreal, under the direction of Professors Maurice Ptito and Jean-François
Bouchard. The study investigated the role of cannabinoid receptors and their endogenous ligands in the visual system.
“Cannabis, also known as hemp name can be in the forms of marijuana and hashish. Consumption affects many biological functions such as memory, motor coordination and appetite. But little is known action of the endocannabinoid system in the vision,” says Joseph Bouskila, which makes the research subject of his thesis. It is concentrated on the CB1 and CB2 receptors, these proteins present naturally in the body.
Recent data are consistent with others in the literature and show that the CB1 receptor modulates vision. “If you block this receptor, the retina becomes more sensitive to light,” summarizes Mr. Bouskila. This had never been shown before by electrophysiological techniques in primates.
Therapeutic properties of cannabis
The first traces of medical use of cannabis derivatives are found in Chinese and Egyptian texts dating from several hundred years before Christ. They are used for millennia to treat pain, spasms, nausea, lack of appetite … “Since the 80s, the use of cannabis as a treatment was delayed because of the psychotropic effects of the product, which was replaced with synthetic derivatives “said Joseph Bouskila.
In the 70s, when psychotropic drugs had better press, observers reported that Jamaican fishermen who smoked cannabis had improved night vision. “Until recently, it was still a story,” says Bouskila. In 2004, researchers scientifically confirmed that the retina is more responsive to stimuli after cannabis. But to date, we still do not know for sure how or why this plant can improve night vision.
Establishing that the endocannabinoid system is present in the primate retina, the work of Joseph Bouskila allow to better understand the physiology of vision and explain photosensitivity caused by marijuana. Thus, it appears that the endocannabinoid system may modulate several functions such as retinal sensitivity and color vision.
This recent discovery opens the way to new treatments for serious illness or incurable, affecting the most sensitive area of the eye, the retina. “Further studies are needed, but our current data indicate that cannabinoids could potentially be useful for treating pigmentary retinitis, says the researcher. Other eye conditions such as glaucoma and macular degeneration related to age could also benefit because they cause, too, degeneration of rods and cones“.
The study of Joseph Bouskila was conducted with monkeys because their neural processing of visual information is similar to that of human beings.
“Studying primate allows us to better understand how the visual system of the human view of the similarity of its anatomical and functional organization,” says Bouskila. The researcher cautions that the monkeys were anesthetized for testing. The research protocol was approved by the Ethics Committee of the University of Montreal.
To achieve observe the effects of endocannabinoids on the visual system, the researcher did not smoke marijuana to primates. Instead, he opted for the combination of two methods, either electroretinogram and injection of a blocker in the vitreous of the eye. These methods are very similar to those used routinely in humans. The first is a consideration of electrical measurement of the eye when a light signal is sent. The second makes it possible to inject the drug near the retina. “As the THC binds to the same receptors CB1 and CB2 that endocannabinoids, they can reproduce all the central and peripheral effects of cannabis,” Mr. Bouskila.
But how to explain the increase in visual sensitivity while subjects were anesthetized? “The retina consists of photoreceptors containing the light-sensitive pigments, meets the researcher. They therefore react to the light beams, the animals are asleep or not. “According to the fact that visual sensitivity monkeys increases together are blocked cannabinoid receptors of the retina shows that there is an endogenous system in place. What is its biological function? This is what probably will uncover his doctoral work completed.