A new study has found that cannabinoids improve low-light vision by increasing the activity in retinal ganglion cells.
Compounds found in cannabis improve vision in low light, according to a new study published in the journal eLife Sciences. Researchers from the Montreal Neurological Institute found that exposure to cannabinoids increased the activity in retinal ganglion cells (RGCs) in tadpoles, thereby improving the transmission of information about light detection from the eye to the brain.
What the researchers, led by professor of neurology and neurosurgery Ed Ruthazer, observed was in opposition to findings in some previous studies, which indicated that cannabinoids actually reduce neurotransmission regarding light detection.
“Initially you distrust yourself when you see something that goes against widely held ideas, but we tried the experiment so many times, using diverse techniques, and it was a consistent result,” says Ruthazer. “So then we knew we had to figure out what was going on. The first tendency is to want to ignore it. But it was such a strong effect, we knew there was something important here.”
What Ruthazer and his team found was that the CB1 endocannabinoid receptor, when activated, reduces chloride levels to hyperpolarize the cell and in turn causes RGCs to fire at higher frequencies. The stimulation caused by cannabinoid exposure allowed tadpoles to greater detect dimmer objects in low light.
CB1 receptors are primarily located in the central and peripheral nervous system. Research has found that tetrahydrocannabinol (THC), the psychoactive natural compound found in cannabis, has a strong binding affinity CB1 receptors, thereby helping to modulate an array of bodily functions like appetite, sleep and anxiety.
In the study, the tadpoles were exposed to increased levels of either exogenous cannabinoids (artificially introduced substances) or endogenous cannabinoids (naturally occur in the body). Both were found to stimulate RGCs.
Whether cannabinoids would have the same vision-improving effect on humans is unknown thus far. However, anecdotal evidence has found cannabis to be effective at improving the night vision of Jamaican and Moroccan fisherman. Additionally, one study found cannabis to effectively prevent vision loss and blindness caused by retinitis pigmentosa. Another found that babies that were exposed to cannabis in the womb were better at tracking moving objects in their line of sight.
“Our work provides an exciting potential mechanism for cannabinoid regulation of neuronal firing, but it will obviously be important to confirm that similar mechanisms are also at play in the eyes of mammals,” said Ruthazer. “Though technically more challenging, a similar study should now be performed in the mouse retina or even in cultures of human retinal cells.”
Both the medical community and general population in the United States are increasingly accepting of the therapeutic benefits of cannabis and its cannabinoids. A recent Quinnipiac University poll found that 89 percent of American registered voters nationwide are in support of medically prescribed marijuana. Twenty-five U.S. states have so far passed comprehensive medical marijuana legislation and several states will be voting on medicinal cannabis initiatives this November.
While the Drug Enforcement Administration recently declined to reschedule cannabis, it did decide to allow more than one national producer of research grade cannabis, which should help improve on at least one of the delay causes that researchers face when studying the therapeutic benefits of cannabis. Hopefully an increase in creditable medical research will further reveal the cannabis’ exciting therapeutic potential. Read more about the groundbreaking findings of cannabis on our Overview of Medical Marijuana page.