Genetics of ethanol-induced locomotor activation: Detection of QTLs in a C57BL/6J x DBA/2J F₂ intercross

Moderate doses of ethanol (1-2 g/kg) markedly increase locomotor activity in some inbred mouse strains, for example, the DBA/2J (D2), but have relatively little effect in other strains, for example, the C57BL/6J (B6). In the present study, we conducted a genome-wide search in a B6D2 F₂ intercross (N = 925) for quantitative trait loci (QTLs) associated with the locomotor response. A QTL with a LOD score of 8.4 was detected on Chromosome (Chr) 2; this QTL accounted for 11.4% of the phenotypic variance and approximately 30% of the genetic variance. The QTL on Chr 2 is in the same general region as QTLs previously described for ethanol preference/consumption (Rodriguez et al. Alcohol Clin Exp Res 19, 367, 1995; Melo et al. Nat Genet 13, 147, 1996; Phillips et al. Mamm Genome, in press), acute ethanol withdrawal (Buck et al. J. Neurosci 17, 3946, 1997) and nitrous oxide withdrawal severity (Belknap et al. Behav Genet 23, 213, 1993). A logical candidate gene in the region of interest is the enzyme which synthesizes GABA, glutamic acid decarboxylase 1 (GadI).