GDNF and Parkinson disease: Alongthis line, we decided to study whether activation of group-II mGlu receptorsinfluences the endogenous production of glial cell line-derived neurotrophic factor(GDNF), which is a potent factor for survival and axonal growth of mesencephalicdopaminergic neurons and has been shown to improve motor symptoms and attenuatenigro-striatal damage in experimental animal models of parkinsonism [22], [23], [24],[25], [26].