Demonstration of disturbed activity of orbitofrontal pyramidal neurons in depressed patients by the AgNOR staining method.

BACKGROUND: The aim to find the morphological biomarker of disturbed activity of the orbitofrontal cortex (OFC) in depression was approached by the karyometric analysis of pyramidal neurons.
METHODS: The study was performed on paraffin-embedded brains from 19 depressed patients from both major depressive disorder (MDD) and bipolar disorder (BD) diagnostic groups, including 9 suicides, and 24 matched controls. The karyometric parameters of medial OFC layer III and V pyramidal neurons bilaterally were evaluated by argyrophilic nucleolar organiser region (AgNOR) silver staining method.
RESULTS: The enlarged nuclear area was found in layer V pyramidal neurons in the right OFC in non-suicides compared to suicides and controls, which was most likely the effect of neuroleptics. The intra-group comparisons between the hemispheres suggest the disturbed orbitofrontal lateralisation in depressed patients (predominantly in suicides) with moderate distinctness of the MDD and the BD diagnostic groups. LIMITATIONS: A major limitation of this study is a relatively small number of cases. A further limitation is given by the lack of data on drug exposure across the whole lifespan.
CONCLUSION: The results suggest disturbed activity of OFC pyramidal neurons in depression, distinct in suicide and the diagnostic groups of mood disorders. The non-suicidal patients seem to benefit from neuroleptics, which most likely increase the activity of the subpopulation of OFC pyramidal neurons.