Neuronal histamine production remains unaltered in Parkinson's disease despite the accumulation of Lewy bodies and Lewy neurites in the tuberomamillary nucleus.

Neuronal histamine production in the hypothalamic tuberomamillary nucleus (TMN) was hypothesized to change significantly in Parkinson's disease (PD) in relation to the accumulation of Lewy bodies/Lewy neurites (LBs/LNs). We measured the messenger ribonucleic acid (mRNA) levels of histidine decarboxylase (HDC), the key enzyme of histamine production, and the amount of LBs/LNs in the TMN by quantitative in situ hybridization and immunocytochemistry in postmortem human brain material of clinical PD (CPD), preclinical PD, and control subjects. No significant difference of histidine decarboxylase mRNA levels was observed among different clinical or Braak-PD stages, in spite of the strong accumulation of LBs/LNs in the TMN of clinical PD patients. We conclude that neuronal histamine production remains largely unaltered in PD despite the abundant LB/LN accumulation in the TMN.