Eye High

The use of cannabis in medicine remains controversial, but there is growing evidence linking it to pain relief and even improved night vision. This slice through a tadpole’s eye shows layers of cells in the retina (each cell has a purple nucleus). These carry visual signals from the outside world (bottom) towards the back of the eye (top) on the way to the brain. The retina is covered in red-coloured receptors (switches) controlled by endocannabinoids, natural chemicals in the body that are similar to those in cannabis. It turns out endocannabinoids boost the 'excitability' of retinal ganglion cells (one shown here in green), which transmit signals to the brain. Tadpoles with switched on cannabinoid receptors have improved vision in low light, hinting at molecular evidence for the effects of cannabis on enhancing human sight in the dark.

Written by John Ankers

John Ankers

Writer

A former researcher in systems biology, John is now an online biology tutor and professional coach supporting the wellbeing of scientists and NHS professionals. He's writing, too, of course.

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• Image from work by Loïs S Miraucourt and colleagues
• Montreal Neurological Institute, McGill University, Montreal, Canada
• Image originally published under a Creative Commons Licence (BY 4.0)
• Research published in eLife, August 2016