Development of congenic rat strains for alcohol consumption derived from the alcohol-preferring and nonpreferring rats.

A genome scan of the F2 generation from an inbred alcohol-preferring (iP) and inbred alcohol-nonpreferring (iNP) rat cross identified a significant quantitative trait locus (QTL) on chromosome 4 with a lod score of 9.2. To confirm this QTL and to create animals for fine mapping of the QTL region, chromosome 4 reciprocal congenic strains were developed by transferring the chromosome 4 QTL interval into the respective iP or iNP backgrounds. The iP strain was crossed with the iNP strain to create iPiNP F1 animals, which were backcrossed to either iNP or iP animals to produce the N2 generation. Using marker-assisted selection, 10 generations of backcrossing were performed. The selection was followed by an intercross between the N10 animals to produce homozygous animals (N10F1), resulting in the finished congenic strains. Congenic strains in which the iP chromosome 4 QTL interval was transferred to the iNP (NP.P) and the iNP chromosome 4 QTL was transferred to the iP (P.NP) exhibited the expected effect on alcohol consumption of the donor strain. Development of these congenic strains further indicates that the chromosome 4 QTL region is, in part, responsible for the disparate alcohol consumption observed between the iP and iNP rats. These congenic animals will be an invaluable resource for fine mapping the QTL region and for the identification of the gene(s) that influences the drinking behavior of the iP and iNP rats.