Post-mortem morphometric studies report reductions in the average density and size of cortical neurons in the dorsolateral prefrontal cortex (dlPFC) and orbitofrontal cortex (ORB) in major depressive disorder (MDD). The contribution of specific neuronal phenotypes to this general pathology in depression is still unclear. Post-mortem sections from the dlPFC and ORB regions of 14 subjects with MDD and 11 controls were immunostained to visualize calbindin-immunoreactive (CB-IR) and parvalbumin-immunoreactive (PV-IR) presumptive GABAergic neurons. A three-dimensional cell counting probe was used to assess the cell packing density and size of CB-IR neurons in layers II + IIIa and PV-IR neurons in layers III-VI. The density of CB-IR neurons was significantly reduced by 50% in depression in the dlPFC and there was a trend toward reduction in the ORB. The size of CB-IR somata was significantly decreased (18%) in depression in the dlPFC with a trend toward reduction in the ORB. In contrast, there was no difference in the density of PV-IR neurons between the depressed and control groups in the dlPFC. The size of PV-IR neuronal soma was unchanged in depressed compared to control subjects in either dlPFC or ORB. In depression, subpopulations of GABAergic neurons may be affected differently in dlPFC and ORB. A significant reduction in the density and size of GABAergic interneurons immunoreactive for calcium binding proteins was found predominantly in the dlPFC region. These cellular changes are consistent with recent neuroimaging studies revealing a reduction in the cortical levels of GABA in depression.

Data from the United States and from several European countries show that patients with major mood disorders, schizophrenia and social phobia smoke at significantly higher rates than the general population. However, there are no published results on this field from Central Europe, including Hungary. In the present study, the rate of current and lifetime smoking of the consecutively screened outpatients with DSM-IV unipolar major depression (n=92), bipolar disorder (n=60), schizophrenia (n=80), schizoaffective disorder (n=42) and panic disorder without major depression (n=60) were assessed and the data were compared to the controls (n=5503), representative for the general population of Hungary. The results showed that, compared to controls, the rates of current and lifetime smoking were significantly higher among patients with unipolar major depression, bipolar disorder, schizophrenia and schizoaffective disorder, but not among patients with panic disorder without major depression. The findings support previous findings from other countries on the strong relationship between cigarette smoking and major mood and schizophrenic spectrum disorders.

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