NTSR1 and Parkinson disease: Although NTSR1 is not a marker of dopaminergic phenotype, this receptor is present in nigral dopaminergic neurons at high density [33], decreases in the substantia nigra of PD patients [55] and of 6-OHDA parkinsonian rats [28], and plays an important role in the modulation of nigrostriatal dopaminergic neurotransmission [56].