Cannabis is about to become a new wonder drug. The active ingredients of the infamous plant have turned out to have the potential to relieve a long series of diseases, from cancer to epilepsy, and now, animal experiments by the Montreal Neurological Institute in Canada indicate that cannabis also benefits vision.
25 years ago, pharmacologist M. E. West of the University of the West Indies in Kingston, Jamaica observed that local fishermen were able to to see in the dark after smoking cannabis or drinking arum made of the leaves and stem  of the plant, enabling thel to to navigate their boats through coral reefs without compass or light. He Wrote  after accompanying the crew of a fishing boat one dark night, “[but] I was then convinced that the man who had taken the rum extract of cannabis had far better night vision than I had, and that a subjective effect was not responsible.” Some of these crew members told West that Moroccan fishermen and mountain dwellers experience the same night vision ability after smoking hashish.

Now, another study provides hard evidence for the claim, revealing a cellular mechanism by which cannabis might improve night vision. The findings, published recently in the open access journal eLife, could eventually be applied to the treatment patients with degenerative eye diseases such as retinitis pigmentosa.
 
West explained that cannabis might improve night vision by acting on the eye muscles to dilate the pupils, so that more light falls in the retina, but experiments showed that marijuana constricts the pupils. It’s also possible that the drug can influence activity in the visual cortex at the back of the brain, but the CB1 receptor protein, which binds the psychoactive ingredient of cannabis, is found at far higher levels in the eye than in the visual cortex, suggesting that any effects the drug has on vision are likely due to its actions on retinal cells.

Lois Miraucourt of the Montreal Neurological Institute and his colleagues looked not to stoned fishermen, but to tadpoles of the African clawed toad, Xenopus laevis, which are transparent and, therefore, amenable to all sorts of experiments that cannot be performed in humans or other lab animals.

In tadpoles, cannabinoids, increase the activity of the retina cells, which become more sensitive to light. It remains unclear, whether the effect is the same in humans, but there is evidence to suggest it. Previously, scientific studies from both Morocco and Jamaica have demonstrated that local mountain peasants and fishermen get markedly improved night vision after consuming cannabis.

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