Micro-positron emission tomography imaging studies were conducted to characterize modulation of metabotropic glutamate subtype-5 receptor (mGluR5) function in a 6-hydroxydopamine (6-OHDA)-induced rat model of Parkinson's disease using four analogical PET ligands: 2-[(11)C]methyl-6-(2-phenylethynyl) pyridine ([(11)C]MPEP), 2-(2-(3-[(11)C]methoxyphenyl)ethynyl)pyridine ([(11)C]M-MPEP), 2-(2-(5-[(11)C]methoxypyridin-3-yl)ethynyl)pyridine ([(11)C]M-PEPy), and 3-[(2-[(18)F]methyl-1,3-thiazol-4-yl)ethynyl]pyridine ([(18)F]M-TEP).