Previous studies have shown behavioral differences between HAP-1 and LAP-1 mice (Grahame et al., 2000; Chester and Barrenha, 2007). While HAP-1 mice showed greater baseline startle responses and PPI than LAP-1 mice, both strains showed similar baseline levels of motor activity. However, since findings from the present study showed that baseline energy ERO activity was not significantly different among HAP-1, LAP-1 and HS/Ibg mice, these different phenotypes do not account for the findings in the present study. Studies by Chester and colleagues (2003) using the taste conditioning procedure showed that HAP-1 and LAP-1 mice also differ in the taste sensitivity to alcohol. QTL analyses in HAP-1 and LAP-1 mice have identified several chromosomal regions containing genes that may play a role in alcohol preference (Bice et al., 2006, 2008). Initial studies in HAP-1 and LAP-1 mice found a QTL on chromosome 9 near the gene that encodes the dopamine D2 receptor, Drd2 (Bice et al., 2006). More recently, Bice et al. (2008) found that alcohol-naive HAP-1 mice showed significantly reduced levels of Drd2 mRNA expression in the nucleus accumbens and
