bob, were're all entitled to our opinions.
if research on rats could always be transferred 100% to humans we would have been "cured" and/or have stopped progression years ago. a lot of pd trials of something that worked in rats have failed in humans.
so i'm not going to take any study on rats too seriously. especially when you can't get a sun tan from a normal fluorescent bulb. and a tan is from producing melanin.
they can grow human dopamine neurons in a petri dish, derived from skin cells from someone with pd. they could test their theory on them but what if the artificial light did inhibit dopamine production, what would you do with that info? it's still a very unnatural situation.
http://en.wikipedia.org/wiki/Melanin