Who needs night vision goggles when you can just smoke a little cannabis?

This is the theory outlined (at least somewhat more scientifically) in a new study published in the journal eLife, which sheds fresh light on the long-held suspicion that cannabis might improve night vision.

The new study has revealed a cellular mechanism that could be responsible for improving your eyesight in the dark after you’ve consumed cannabis. To reach this conclusion, Lois Miraucourt of the Montreal Neurological Institute and his colleagues examined tadpoles of the African clawed toad – whose transparent nature makes them the perfect subjects for experiments that cannot be performed on humans or other lab animals.

In one set of tests, the researchers applied a synthetic cannabinoid to eye tissue preparations from the tadpoles, and proceeded to use microelectrodes to measure how retinal ganglion cells (whose fibres form the optic nerve) respond to light. What they discovered was that this made the cells more sensitive, increasing the rate that they fired both bright and dim light stimuli. This took place thanks to the inhibition of a protein called NKCC1, via its actions on the CB1 receptor. NKCC1 is a co-transporter of protein that typically moves sodium, potassium and chloride ions in and out of cells, and their concentrations influence the electric properties of nerve cells.

On a broad scale, these experiments demonstrate that cannabinoids reduce the concentration of chloride ions within the retinal ganglion cells, causing them to be more excitable and more sensitive to light.

The researchers carried out another set of tests to figure out whether the cellular responses they observed could have an effect on vision.

Since tadpoles naturally tend to avoid dark moving dots, the researchers exploited this by putting some tadpoles in a Petri dish and showing them dark dots under various lighting conditions. They did this while using special video-tracking software to track the movements of the tadpoles and the dots, and to measure the tadpoles’ avoidance responses.

While they observed no differences between tadpoles treated with a synthetic cannabinoid and untreated ones under normal lighting conditions, they noticed something decidedly different in the dark. When the lights were down, tadpoles given the cannabinoid avoided considerably more dots than untreated ones, which only responded to the dots as if by chance. The researchers then concluded that the enhanced cellular responses seen in the first set of tests improved the tadpoles’ sensitivity to contrast in low-light conditions.

It’s still unknown whether these findings could be applicable to humans, but if they are, they could influence treatments for degenerative eye diseases like retinitis pigmentosa and glaucoma. Since cannabinoids are known to have a neuroprotective effect on retinal cells, treatments based on the drug may not only improve vision but also decrease the rate at which such diseases progress. 

h/t The Guardian.