Schizophrenia and bipolar disorder show both common and distinct changes in cortical interneuron markers

Area of Science:

• Neuroscience
• Psychiatry
• Molecular Biology

Background:

• Schizophrenia and bipolar disorder are distinct psychotic disorders with overlapping neuropathologies.
• Cortical interneurons are implicated in both conditions, but specific interneuron population contributions remain unclear.

Purpose of the Study:

• To investigate the relative contribution of distinct interneuron populations to schizophrenia and bipolar disorder at the molecular level.
• To identify shared and unique interneuron marker alterations in the prefrontal and orbitofrontal cortices of patients with schizophrenia and bipolar disorder.

Main Methods:

• Quantitative analysis of messenger RNA (mRNA) levels for specific interneuron markers (somatostatin, vasoactive intestinal peptide, calbindin).
• Comparison of mRNA levels in prefrontal and orbitofrontal cortical tissue samples from patients with schizophrenia (n=35), bipolar disorder (n=31), and healthy controls (n=34).

Main Results:

• Reductions in somatostatin and vasoactive intestinal peptide mRNAs were observed in both bipolar disorder and schizophrenia groups compared to controls.
• An increase in calbindin mRNA was found specifically in the schizophrenia group.

Conclusions:

• Shared molecular deficits in specific interneuron markers indicate common neuropathological pathways in schizophrenia and bipolar disorder.
• The unique increase in calbindin mRNA in schizophrenia suggests distinct molecular alterations contributing to this disorder.