P2RX7 and Parkinson disease: P2X purinoceptor 7 (P2X7) receptors widely exist in microglia, astrocytes, and oligodendrocytes, and they regulate the neuronal function of the central nervous system of PD by releasing proinflammatory cytokines/chemokines, ROS, and the excitotoxic gliotransmitters glutamate and ATP.