1. ¹UNC Schizophrenia Research Center, Chapel Hill, NC, USA
2. ²Department of Psychiatry, Chapel Hill, NC, USA
3. ³Department of Cell and Developmental Biology University of North Carolina at Chapel Hill, Chapel Hill, NC, USA

Correspondence: JH Gilmore, Department of Psychiatry, CB# 7160, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7160, USA. Tel: +1-919-966-6971; Fax: +1-919-966-8994; E-mail: jgilmore@med.unc.edu

Received 17 November 2003; Revised 22 February 2004; Accepted 18 February 2004; Published online 7 April 2004.

Abstract

Prenatal exposure to infection increases risk for schizophrenia, and we have hypothesized that inflammatory cytokines, generated in response to maternal infection, alter neuron development and increase risk for schizophrenia. We sought to study the effect of cytokines generated in response to infection—interleukin-1 (IL-1), tumor necrosis factor- (TNF), and interleukin-6 (IL-6)—on the dendritic development of cortical neurons. Primary mixed neuronal cultures were obtained from E18 rats and exposed to 0, 100, or 1000 units (U)/ml of IL-1, TNF, IL-6, or IL-1+TNF for 44 h. MAP-2-positive neurons were randomly identified for each condition and the number of primary dendrites, nodes, and total dendrite length was determined. We found that 100 U of TNF significantly reduced the number of nodes (27%, p=0.02) and total dendritic length (14%, p=0.04), but did not affect overall neuron survival. A measure of 100 U IL-1+TNF significantly reduced the number of primary dendrites (17%, p=0.006), nodes (32%, p=0.001), and total dendritic length (30%, p<0.0001), although it did not affect overall neuron survival. At 1000 U, each cytokine significantly reduced the number of primary dendrites (14–24%), nodes (28–37%), as well as total dendritic length (25–30%); neuron survival was reduced by 14–21%. These results indicate that inflammatory cytokines can significantly reduce dendrite development and complexity of developing cortical neurons, consistent with the neuropathology of schizophrenia. These findings also support the hypothesis that cytokines play a key mechanistic role in the link between prenatal exposure to infection and risk for schizophrenia.