SIMILAR DEFICITS OF CENTRAL HISTAMINERGIC SYSTEM IN PATIENTS WITH DOWN-SYNDROME AND ALZHEIMER-DISEASE

In order to study whether Alzheimer-like neuropathological changes inv olve the central histaminergic system we measured the concentration of histamine, its precursor histidine as well as the activity of histidi ne decarboxylase (HDC) and histamine-hi-methyltransferase (HMT) in fro ntal cortex of aging Down syndrome (DS) patients, Alzheimer patients a nd control individuals. The study populations were also investigated f or choline acetyltransferase (ChAT) activity, since reduced ChAT activ ity is an established biochemical hallmark in DS and Alzheimer disease (AD). HDC and ChAT activity were reduced in brains of both DS and Alz heimer patients versus control patients. Additionally, we observed a s ignificant decrease of histamine levels in the DS group, Histamine lev els in AD brains tended to be decreased, Histidine concentrations and HMT activities were comparable between the three groups. Thus, our res ults for the first time show histaminergic deficits in brains of patie nts with DS resembling the neurochemical pattern in AD. Neuropathologi cal changes may be responsible for similar neurochemical alterations o f the histaminergic system in both dementing disorders. (C) 1997 Elsev ier Science Ireland Ltd.