Neuropeptide Y Y₁ and Y₂ receptor mRNA expression in the prefrontal cortex of psychiatric subjects: Relationship of Y₂ subtype to suicidal behavior

It has been hypothesized that the neuropeptide Y (NPY) system is involved in the pathogenesis of mood disorder. In this study, Y₁ and Y₂ receptor mRNA expression levels were analyzed in the dorsolateral prefrontal cortex of subjects affected with major depression, bipolar disorder, or schizophrenia and compared to normal controls. No significant alterations in Y₁ or Y₂ mRNA expression levels were observed between the groups. However, the Y₂ mRNA expression was elevated in layer IV in subjects with suicide as a cause of death. For the Y₁ mRNA expression, there was a negative correlation with increasing subject age in the prefrontal cortex. Analysis of covariance revealed a significant elevation of the Y₁ mRNA expression levels in individuals with a current history of marijuana use but no other drug. In summary, the current results suggest distinct alterations of the prefrontal Y₁ and Y₂ neuronal populations in aging and suicide.