Development of reciprocal congenic strains. Alcohol-preferring (P) and alcohol-nonpreferring (NP) rats were selectively bred for high and low alcohol drinking from a closed colony of Wistar rats . Inbreeding was initiated at generation 30 to create the inbred P (iP) and iNP rats . Chromosome 4 reciprocal congenic rats were developed in which the iP chromosome 4 QTL interval from D4Rat119 to D4Rat55 was transferred to the iNP (NP.P-(D4Rat119-D4Rat55)) and the iNP chromosome 4 QTL interval was transferred to the iP (P.NP-(D4Rat119-D4Rat55)) . Genotyping of D4Rat15, D4Rat119, D4Rat55, and D4Rat 192 revealed that the recombination location was between D4Rat15 and D4Rat119 and between D4Rat55 and D4Rat192 .