The test of two-bottle DID intake was consistent with previous studies with inbred mice. Multiple inbred strains of mice were given three DID tests, each lasting 4 days. The first two, a week apart, were with a single ethanol bottle. The final test, 2 weeks later, was with two bottles (ethanol vs. water). In that study, mean strain intake of ethanol was quite stable across all three tests. However, mice also drank some water in the two-bottle test, and mean BECs were considerably lower than in the single-bottle DID test (13). Given that only about 43% of animals in the HDID-1 line were drinking to intoxication by S9, it is perhaps understandable that the phenotype did not generalize to a two-bottle choice situation in S9. However, we plan to test future generations on a regular basis as their DID response becomes more extreme.
