The interesting observation of scientist M.E. West of the University of the West Indies in Kingston, Jamaica, 25 years ago is still causing ripples in the scientific world of cannabinoids to this day.
The Guardian’s Science editor reports on the latest findings of hard evidence revealing the cellular mechanism by which cannabis could improve night vision.
Fishermen and transparent tadpoles
After West accompanied some fishermen smoking cannabis, and drinking rum made from the stems and leaves of the plant in the waters of Jamaica, he noted it was uncanny how well these fisherman could see in the dark. He remarked: “It should be impossible to navigate a boat through these coral reefs without a compass and lights in these treacherous waters.”
He later discovered Moroccan fishermen and mountain dwellers are also known for similar improvements in night vision after smoking hashish. In 2002, a research team investigated the inhabitants of the mountains in Morocco. They gave synthetic cannabinoids to a volunteer, and some hashish to three others. The sensitivity of their night vision was measured before and after. West’s observations were confirmed, cannabis improved night vision.
West at first thought cannabis dilates the pupil so that more light falls on the retina, but it was found marijuana actually constricts the pupils. The search for an explanation was on, and Lois Miraucourt of the Montreal Neurological Institute and his colleagues took on the challenge.
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Frogs from Africa
They didn’t use people to test cannabis, but transparent frogs from Africa. Miraucourt and his team applied synthetic cannabinoids to one set of eye tissue preparations, measuring retinal ganglion cells’ response to light with microelectrodes. The cells were more sensitive to bright light, as well as dim stimuli. They discovered this was due to inhibition of a protein NKCC1, which acts on the CB1 receptor. NKCC1 usually carries sodium, potassium and chloride ions in and out of cells, which determines the electrolyses of nerve cells.
The conclusion was that cannabinoids reduce the concentration of chloride ions in the retinal ganglion cells, which makes them more sensitive and excitable to light.
Tadpoles in Petri dishes
Further experiments were done on tadpoles avoiding dark spots in Petri dishes under different sets of lighting conditions. In the dark, tadpoles given synthetic cannabinoids avoided significantly more dark spots than untreated tadpoles. Specially designed video-tracking software was used to track the movements of the tadpoles in relation to the dots, and to measure the tadpoles’ avoidance responses.
Cannabinoids not only improve night vision
If these ingenious findings could be applied to humans it could pave the way to treatments for diseases such as retinitis pigmentosa and glaucoma. Cannabinoids are known to have a neuroprotective effect on retinal cells. In theory they will then not only improve vision of patients with deteriorating eyesight, but also slow down the progress of the disease.