SLC6A4 and Parkinson disease: The aim of the present study was to investigate how neural networks related to the main brain neurotransmitter transporters (DAT, NET, SERT) and metabotropic glutamate receptor 5 (mGluR5), affect the perception of fatigue in a cohort of 35 PD patients, including 18 with clinically significant fatigue (FAT) and 17 without (NFAT).