Anxiety in genetically heterogeneous rats: Towards the identification of quantitative genes for behavioural traits

The use of genetically heterogeneous (outbred) rodents is a unique resource for the identification and fine mapping of genetic loci (QTL) influencing biological and behavioural quantitative phenotypes, allowing the identification of quantitative genes. We present the first study of this kind carried out with genetically heterogeneous rats (N/Nih-HS; derivated from an eight-way cross of inbred strains), whose behaviour is assessed in tests evoking unlearned (Black/white box, Elevated "zero" maze) or learned (context conditioned freezing, two-way active avoidance acquisition in the shuttlebox) anxious/fearful responses. The behavioural profile of N/Nih-HS rats is more similar to that of RLA-I (anxious) rats rather than to RHA-I (low anxious) rats. Significant correlations are found among unconditioned anxiety variables and two-way active avoidance acquisition in the shuttlebox; these are partially confirmed by multiple regression analysis. "High avoider" N/Nih-HS rats show lower unlearned anxiety levels than "low avoiders". Results of this behavioural assessment of the N/Nih-HS rats are discussed in terms of their potential usefulness for present and future neurobehavioural and genetic studies of fearfulness and anxiety. © Copyright 2009: de los Editores de Ansiedad y Estrés