Identification of quantitative trait loci for anxiety and locomotion phenotypes in rat recombinant inbred strains

Anxiety disorders are phenotypically complex and may involve multiple genetic influences on many neurotransmitter systems. Rodent tests used to investigate genetic influences on anxiety-like phenotypes have face and predictive validity as models for anxiety in humans. If multiple genes contribute additively to a trait, the trait will be continuously distributed and be amenable to detection of associations between allelic variation at specific chromosomal loci and the phenotypes being studied via quantitative trait loci (QTL) mapping. The elevated plus-maze test provides quantitative measures of both anxiety-like and locomotion phenotypes. Using this test, we assessed four phenotypes in a set of 22 rat recombinant inbred (RI) strains derived from Brown Norway (BN.Lx/Cub) and Spontaneously Hypertensive rat (SHR/Ola) progenitors. QTL analyses were used to determine whether allelic variation at specific chromosomal loci contribute significantly to RI strain-dependent variance in each phenotype. Significant QTL for an anxiety phenotype were found on chromosomes 2, 5, 6, and 7. For a phenotype reflecting both anxiety and locomotion, QTL were found on chromosomes 2, 7, and 8, while for a locomotion phenotype, significant QTL were found on chromosomes 3 and 18.