Reductions in neuronal density in elderly depressed are region specific

Frontal regions, including the orbitofrontal cortex (ORB) and dorsolateral prefrontal cortex (dlPFC) have been implicated in the neuropathology of geriatric depression. Prominent reductions in pyramidal neuron density have been recently reported in the ORB of older depressed subjects. However, the cellular pathology of the dlPFC has not yet been examined in these subjects.

Postmortem tissue from the dlPFC (Brodmann's area 9, BA9) was collected from 10 older (>60 years old) subjects diagnosed with major depression and 10 age-matched non-psychiatric controls (CTRL). The majority of the subjects were the same as those used for our previous study on neuronal reductions in the ORB in older depressed. Overall (all six layers combined), and laminar density of pyramidal (presumably glutamatergic), and non-pyramidal (GABAergic) neurons as well as cortical and laminar width were measured using linear optical disector of Stereoinvestigator software.

Neither the overall nor laminar density of pyramidal or non-pyramidal neurons was significantly different between groups. The cortical and laminar widths were also not affected.

These results suggest that neuronal prefrontal pathology in elderly depressed is region specific. No significant changes were detected in the density of any type of neurons in the dlPFC of elderly depressed subjects (present study) whereas, prominent reductions in the density of pyramidal glutamatergic neurons were observed previously in the ORB.