GPR55 and Parkinson disease: Later on, strong neuroprotective properties in PD were found for those cannabinoids active against inflammation and glial reactivity, whose effects are exerted through the activation of the cannabinoid type-2 (CB2) receptor [15,16,17,18], but also targeting the peroxisome proliferator-activated receptor-γ (PPAR-γ) [19,20] and the G protein-coupled receptor 55 (GPR55) [21].