Melanopsin was originally discovered by Ignacio Provencio and his colleagues in 1998, in the specialized light sensitive cells of frog skin.
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The first recordings of light responses from melanopsin-containing ganglion cells were obtained by David Berson and colleagues at Brown University.
In 2002, Samer Hattar and colleagues, including David Berson, showed that in the rat, intrinsically photosensitive retinal ganglion cells invariably expressed melanopsin.