Study finds pot improves night vision — in tadpoles
Montreal researchers have found a new role for cannabinoids. The active ingredient in marijuana — which is also naturally present in the human body — seems to improve night vision in vertebrates.
The study by a multidisciplinary team including researchers from the Montreal Neurological Institute looked at changes in tadpole retinas after exposure to cannabinoids.
“We didn’t believe what we were seeing — exactly the opposite of what we expected,” said neurologist Ed Ruthazer, of the Montreal Neurological Institute of McGill University, and the paper’s senior author.
Researchers expected to find the drug would inhibit the tadpoles’ retinal ganglion cells (RGCs), which are responsible for transmitting information about light detection from the eye to the brain.
“But the cannabinoids were increasing the excitability of cells in the eye that connects to the brain,” Ruthazer said. One class of cannabinoid receptor, known as CB1, fired at higher frequencies allowing the tadpoles swimming in a petri dish to see better and flee predators in low light conditions, he explained.
Published on Aug. 8 in the journal eLife, a peer-reviewed open-access scientific journal for biomedical and life sciences, the study adds to the understanding of cannabinoids and brain function.
It’s not known whether the same mechanism in the frog eye applies to human eyes, Ruthazer said, however, structurally, there is an evolutionary link.
While it’s too early to say whether cannabinoids have the same effect on mammals, and specifically human vision, some evidence in the scientific literature suggests that it may.
Although some people find that smoking pot makes their vision fuzzy, anecdotal evidence from a 2004 study documented an improvement in night vision among Jamaican fishermen, and Moroccan fishermen and mountain dwellers.
A 2014 study in rats by Pedro Lax of Alicante, Spain found the drug protects against degeneration of the retina by preserving its cones and rods, the structure of the eye that responds to light.
Last year on ResearchGate, a website that connects millions of science-minded researchers, a blind Harvard University student posted a note about her paper, Mending The Mirror, describing how marijuana “gives me some access to vision by stimulating the endocannabinoid system found in the retina and brain. I would like to know if marijuana has improved the vision of others with retinal blinding diseases,” and seeking collaborators for further research on the topic.
Beyond a key role in vision, Ruthazer says he is excited his team has discovered a previously unknown role for cannabinoids in brain signalling. With greater focus on medical marijuana, accurate information on how cannabinoids alter the way cells interact is crucial, he said. The next step, he said, would be testing the signalling mechanism in mouse models and in human retinas grown or cultured from stem cells.
Ruthazer’s study got funding from the Canadian Institutes of Health Research, Fonds de recherche du Québec — Santé, Épilepsie Canada, and a Natural Sciences and Engineering Research Council CREATE Neuroengineering Training Grant.