Altered myelination of the hippocampal formation in subjects with schizophrenia and bipolar disorder.

Myelination of the frontal and temporal lobes occurs at a similar time period as symptom onset in schizophrenia. To assess this potential relationship, we compared myelination and oligodendrocyte numbers in the hippocampal formation of controls and matched subjects with schizophrenia and bipolar disorder. The levels and distribution of the myelin marker myelin basic protein (MBP) and the oligodendrocyte marker adenomatous polyposis coli (APC) were measured using immunocytochemistry. MBP immunoreactivity (IR) was increased in several hippocampal subregions of control females versus control males. Female subjects with schizophrenia and bipolar disorder exhibited decreased myelination in the hippocampal formation while male subjects with bipolar disorder showed increased MBP levels in the superior medullary lamina. In contrast, the number of APC immunoreactive cells did not differ in any disorder or region. Our results demonstrate an interaction between gender, mental illness, and myelination, and may be related to cognitive deficits seen in schizophrenia and bipolar disorder.