Interestingly, ghrelin, an endogenous ligand for growth hormone secretagogue receptor 1a, was demonstrated to prevent the activation of microglia, the production of pro-inflammatory factors (e.g., TNF-α and IL-1β) and the activation of iNOS, and to attenuate dopaminergic neuron loss in the MPTP-induced mouse models of PD (Jiang et al., 2008; Moon et al., 2009). This evidence concerns the gene NOS2 and Parkinson disease.