Decrease of the D4 dopamine receptor messenger RNA expression in lymphocytes from patients with major depression.

Objectives: The evaluation of the possible role of dopamine in psychiatric disorders has been limited by the relative inadequacy of tools. A tempting approach to examine alterations of dopaminergic system in major depression is to examine the expression of dopamine receptors in peripheral blood mononuclear cells (PBMC).
Methods: D4 dopamine receptor (D4DR) messenger RNA (mRNA) expression in PBMC from 12 patients with major depressive disorder was examined before and after an 8-week treatment with paroxetine at 20-50 mg/day. Ten healthy subjects were analyzed in parallel. The relative content of D4DR mRNA was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). using beta-actin as internal standard.
Results: D4DR mRNA levels were significantly decreased in untreated depressed patients as compared to controls. D4DR mRNA expression returned to control levels after paroxetine treatment, when patients achieved a significant improvement of depressive symptoms.
Conclusions: Results of our study suggest the role of PBMC D4DR mRNA expression as a peripheral marker of the central dopaminergic function in major depression.