Neuron density and serotonin receptor binding in prefrontal cortex in suicide

Area of Science:

• Neuroscience
• Psychiatry
• Neurobiology

Background:

• Prefrontal cortex (PFC) alterations in serotonin receptors and cytoarchitecture are noted in depression and suicide.
• Previous studies have not assessed serotonin binding relative to neuron density in the PFC.

Purpose of the Study:

• To investigate neuron density and serotonin transporter (SERT), 5-HT1A, and 5-HT2A binding in the PFC of suicides compared to controls.
• To determine the binding index (receptor binding relative to neuron density) in different PFC regions.

Main Methods:

• Matched pairs of suicides and normal controls (n=15) were psychiatrically assessed.
• Neuron density and binding were quantified using stereology and quantitative autoradiography in Brodmann areas 9 and 47 of the PFC.
• Binding index was calculated as the ratio of receptor binding to neuron density.

Main Results:

• Suicides exhibited lower neuron density in both dorsal (BA 9) and ventral (BA 47) PFC.
• The SERT binding index was lower in BA 47, while the 5-HT1A binding index was higher in BA 9 in suicides.
• SERT binding negatively correlated with 5-HT1A binding in BA 47 in suicides.

Conclusions:

• Individuals who died by suicide show reduced neuron density and altered SERT and 5-HT1A binding in the PFC.
• Findings suggest post-synaptic 5-HT1A receptor up-regulation independent of neuron density changes.
• Cortical abnormalities in both neurons and serotonergic innervation are present in suicides.