Our in vivo studies in rodents support the presence of both drug targets, the receptors for GIP and GLP-1, in brain across age, reported here for the first time, and additionally demonstrated the preservation of these receptors in striatum following a 6-OHDA unilateral medial forebrain bundle lesion as well as in human PD brain (Fig. 1). This evidence concerns the gene GCG and Parkinson disease.