Mechanistically, selective β2AR activation suppresses the degeneration of nigral dopamine neurons, prevents loss of striatal dopamine, and rescues movements in multiple rodent models of PD.6,40,41 Molecularly, β2 agonists reduce α-synuclein expression6,42 and microglial activation.41 Epidemiologically, the significant association between β2-agonists and the risk of PD was confirmed in a recent meta-analysis.43 However, there remains considerable controversy regarding the interpretation of the epidemiologic association (for discussion, see References 44-References 46). This evidence concerns the gene ADRB2 and Parkinson disease.