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Eye High
27 October 2016

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

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BPoD stands for Biomedical Picture of the Day. Managed by the MRC Laboratory of Medical Sciences until Jul 2023, it is now run independently by a dedicated team of scientists and writers. The website aims to engage everyone, young and old, in the wonders of biology, and its influence on medicine. The ever-growing archive of more than 4000 research images documents over a decade of progress. Explore the collection and see what you discover. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.

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