Interest in the relation between ghrelin and Parkinson’s began with the observation that ghrelin could protect striatal dopaminergic neurons, which express the GHSR, from degeneration caused by the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) [190], possibly by preventing the activation of microglia [191]. The gene discussed is GHRL; the disease is Parkinson disease.