Unaltered histaminergic system in depression: a postmortem study.

Area of Science:

• Neuroscience
• Psychiatry
• Molecular Biology

Background:

• Rodent studies suggest the neuronal histaminergic system's role in depression symptoms.
• Histamine is a key neurotransmitter implicated in various brain functions.

Purpose of the Study:

• To investigate the expression of histamine-producing and degrading enzymes, and histamine receptors in the postmortem brain tissue of mood disorder patients.
• To determine if the histaminergic system is altered in major depression disorder (MDD) and bipolar disorder (BD).

Main Methods:

• Quantitative in situ hybridization was used to measure histidine decarboxylase (HDC) expression in the tuberomamillary nucleus (TMN).
• Quantitative PCR (qPCR) assessed the expression of four histamine receptors and histamine N-methyltransferase (HMT) in the dorsolateral prefrontal cortex (DLPFC) and anterior cingulated cortex (ACC).
• Postmortem brain tissue from 12 mood disorder patients (8 MDD, 4 BD) and 12 controls was analyzed.

Main Results:

• No significant changes in HDC or histamine receptor expression were observed between patient groups and controls.
• A significant decrease in histamine N-methyltransferase (HMT) mRNA expression was found in the anterior cingulated cortex (ACC) of MDD subjects.
• The findings suggest a specific alteration in histamine metabolism in the ACC of individuals with MDD.

Conclusions:

• The neuronal histaminergic system, including its production enzyme and receptors, did not show widespread alterations in MDD and BD.
• A notable exception was the reduced HMT mRNA expression in the ACC of MDD patients, indicating a potential role in depression pathophysiology.
• Potential confounding factors like medication and cause of death were considered and did not appear to influence the results.