Gene expression and neuronal activity in schizophrenia: a study of polyadenylated mRNA in the hippocampal formation and cerebral cortex.

The abundance of polyadenylated messenger RNA (poly(A)+mRNA) reflects overall gene expression and provides an index on neuronal activity. Poly(A)+mRNA was measured in the hippocampal formation and in occipital, temporal, cingulate and frontal cortices (Brodmann areas 17, 22, 24 and 46, respectively) of 11 schizophrenic and 17 control subjects post mortem by in situ hybridization histochemistry with a 35S-oligodeoxythymidine probe. There were no differences in poly(A)+mRNA between cases and controls, except for a modest decrease in the parahippocampal gyrus of the schizophrenics which may be attributable to cytoarchitectural differences in this area in the disease. The unchanged level of poly(A)+mRNA in all other regions argues against the existence of a widespread or sustained alteration in the metabolic activity of cortical neurons in schizophrenia. It also provides a further indication that the differential expression of individual transcripts reported in the disease is not merely reflecting changes in overall gene expression.