Discussion of nunuphar's comment: In the main figures, they show only a very small inset with co-labeling of TH and ChR, and I don’t know what to make of this figure because there seems to be a large region of green ChR labeling that is not yellow (i.e. not co-labeled with TH). This suggests that many of their infected cells were not actually TH positive, and may have been GABAergic or neurons of surrounding brain regions. I have also recently heard that the Cre expression in TH-Cre rats is not specific to DA neurons.