GCG and Parkinson disease: In line with this, saxagliptin, which raises levels of both GLP-1 and GIP, has been shown to elevate brain dopamine levels in a rat model of Parkinson disease (PD) [52]; restore levels of both serotonin and dopamine in rodents exposed to anesthesia post stroke [53]; and normalize serotonin, dopamine, and norepinephrine levels in chronically stressed rats [54].