NPY mRNA expression in the prefrontal cortex: Selective reduction in the superficial white matter of subjects with schizoaffective disorder

Background: Alterations in the inhibitory circuitry of the dorsolateral prefrontal cortex (DLPFC) in schizophrenia include reduced expression of the messenger RNA (mRNA) for somatostatin (SST), a neuropeptide present in a subpopulation of gamma-aminobutyric acid (GABA) neurons. Neuropeptide Y (NPY) is expressed in a subset of SST-containing interneurons and lower levels of NPY mRNA have also been reported in schizophrenia spectrum disorders. However, whether the alterations in these two transcripts identify the same, particularly vulnerable, subset of GABA neurons has not been examined. Methods: We used in situ hybridization to quantify NPY mRNA levels in DLPFC gray and white matter from 23 pairs of subjects with schizophrenia or schizoaffective disorder and matched normal control subjects; results were compared to those from a previous study of SST mRNA expression in the same subjects. Results: In contrast to SST mRNA, NPY mRNA levels were not significantly lower in the gray matter of subjects with schizophrenia or schizoaffective disorder. However, NPY, but not SST, mRNA expression was significantly lower in the superficial white matter of subjects with schizoaffective disorder. Conclusion: These findings suggest that the alterations in SST-containing interneurons in schizophrenia and schizoaffective disorder are selective for the subset that do not express NPY mRNA, and that lower NPY mRNA expression in the superficial white matter may distinguish subjects with schizoaffective disorder from those with schizophrenia. (C) 2009 Elsevier B.V. All rights reserved.