The expression of histamine receptor 1-4 (H1- 4R) and histamine methyltransferase was determined in the histamine projection areas which are strongly involved in Parkinson’s disease (PD), i.e. the substantia nigra and striatum, with quantitative polymerase chain reaction and immunocytochemistry. In addition, the relationship between the expression of these molecules and PD pathologies and disease course were analyzed. We found for the first time brain-area-specific changes of neuronal histaminergic system in PD. This may provide scientific evidence for novel therapeutic strategies. The paper was published in Neurobiology of Aging.