METHODS: Therefore, we performed a first postmortem analysis on this topic in the hippocampus--which is of major importance for emotional and cognitive aspects of affective disorders. S100B-immunopositive astrocytes and oligodendrocytes were evaluated in the alveus and the CA1 pyramidal layer of patients with major depressive disorder (MDD) or bipolar I disorder (BD) compared to controls.
RESULTS: As revealed by the optical disector cell-counting method, the numerical density of S100B-immunopositive astrocytes was bilaterally decreased in the CA1 pyramidal layer of MDD and BD patients compared to controls, whereas only the bipolar group showed a decreased density of S100B-immunopositive oligodendrocytes in the left alveus. These results were not confounded by gender, age, duration of disease, medication dosage, or autolysis time.
CONCLUSIONS: Confirming the idea of previous S100B serum and cerebrospinal fluid studies, our data suggest that S100B-immunopositive glia is dysregulated in the brains of depressed patients. These findings are in accordance with animal experiments in rodents showing a reduced astrocytic S100B-immunoreactivity in the hippocampus after pharmacological serotonin depletion (modeling depression).