Science Daily reports on a multi disciplinary team of researchers looking into cannabinoids for eye health.
Cannabinoids for eye health. Who needs carrots?
Researchers across different disciplines teamed up at Montreal Neurological Institute to improve the understanding of how the active agents in cannabis, called cannabinoids, affect vision.
A variety of methods were used to test the reactions of tadpoles to visual stimuli when they received higher levels of exo- and endogenous cannabinoids. Exogenous cannabinoids are artificially administered, and endogenous occur naturally in the body.
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Contrary to what was believed
It was discovered that contrary to what was believed, if cannabinoid signaling was activated, activity increased in RGCs, or the retinal ganglion cells, which transmit information about light awareness or detection to the brain from the nerves in the eye. In the past it was believed cannabinoids reduced neurotransmission, not increase it.
Ed Ruthazer senior author and professor of neurology and neurosurgery at the Montreal Neurological Institute of McGill University says they couldn’t believe the finding, as it goes against widely held ideas. They did the experiment over and over, using diverse techniques to check their findings. The results were consistent, and they knew they had to figure out what was going on. He said at first they wanted to ignore the findings, but the effect was so strong they knew they were onto something important.
They found one class of cannabinoid receptor known as CB1R is involved in suppressing chloride transport to the RGCs. The chloride levels are reduced when the receptors are activated. The cell becomes hyperpolarized, firing higher frequencies when stimulated.
Cannabinoids improve night vision
This means the tadpoles in the study was able to detect objects in dimmer, low light when they were exposed to higher levels of cannabinoids. Software developed by Professor Paul Wiseman of the physics and chemistry department at McGill was used to detect changes in the behavior of the tadpoles.
Anecdotal evidence suggests the same effect in humans, as scientific literature on improved night vision of Jamaican and Moroccan fishermen ingesting cannabis reported better sight at night.
Cannabinoids in brain signaling
Ruthazer says what is even more interesting is that they have uncovered an unknown role of cannabinoids in brain signaling. Cannabinoids are becoming more accepted in therapeutic use by the medical fraternity. The need to understand the working of these chemicals’ role in the brain is becoming more urgent.
He says their work holds exciting potential to discover the mechanism of cannabinoid regulation and neuronal firing, but it is important to establish and confirm similar working in the eyes of mammals. This is a challenge, and it will be technically more difficult to conduct similar studies in mice or cultures of human retinal cells.
Cannabinoids for eye health
The current status of cannabis in the treatment of glaucoma is also being researched as marijuana becomes more available in the USA. Many states have passed laws allowing medicinal or recreational cannabis.
The pharmacology of marijuana and its effect on intraocular pressure has not advanced much since research in the 1970s and 1980s, even though the levels of THC have increased from 2-3% to up to 20% since then. Cannabis is an effective ocular hypotensive agent, however, it also affects cardiovascular and neurological intraocular pressure by reducing ocular blood flow.