1. ¹Department of Pediatrics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
2. ²Department of Anesthesiology and Critical Care Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA, USA

Correspondence: Dr RJ Valentino, Department of Pediatrics, The Children's Hospital of Philadelphia, 402C Abramson Pediatric Research Center, 34th Street & Civic Center Boulevard, Philadelphia, PA 19104-4399, USA. Tel: +1 215 590 0650; Fax: +1 215 590 3364; E-mail: valentino@email.chop.edu

Received 27 December 2005; Revised 3 March 2006; Accepted 5 April 2006; Published online 17 May 2006.

Abstract

The Wistar–Kyoto (WKY) rat is stress sensitive and exhibits depressive-like behavior. The locus coeruleus (LC)–norepinephrine and dorsal raphe (DR)–serotonin systems mediate certain aspects of the stress response and have been implicated in depression. Microarray technology was used to identify gene expression differences in the LC and DR between WKY vs Sprague–Dawley (SD) rats that might account for the WKY phenotype. RNA was isolated from microdissected LC and DR, amplified, and hybridized to microarrays (1 array/subject, n=4/group). Significance of microarray (SAM) analysis revealed increased expression of 66 genes in the LC and 19 genes in the DR and decreased expression of 33 genes in the DR of WKY rats. Hierarchical clustering identified differences in gene expression profiles of WKY vs SD rats that generally concurred with SAM. Notably, genes that encoded for enzymes involved in norepinephrine turnover, amino-acid receptors, and certain G-protein-coupled receptors were elevated in the LC of WKY rats. The DR of WKY rats showed decreased expression of genes encoding several potassium channels and neurofilament genes. The chromosomal locations of 15 genes that were differentially expressed in WKY rats were near loci identified as contributing to depressive-like behaviors in the rat. The specific genes revealed by the present analysis as being differentially expressed in WKY rats may contribute to their unique behavioral profile and suggest targets that confer susceptibility to stress-related psychiatric disorders.